Dermal characteristics of the raw stock and leather in wet blue ...

Journal of Scientific Research and Studies Vol. 3(8), pp. 167-173, August, 2016 ISSN 2375-8791 Copyright © 2016 Author(s) retain the copyright of this article http://www.modernrespub.org/jsrs/index.htm

Full Length Research Paper

Dermal characteristics of the raw stock and leather in wet blue of camel (Camelus dromedarius) hide

Gbolagunte G. D.

Department of Biological Science, Crawford University, Igbesa, Ogun State, Nigeria. E-mail: gbola_akande [email protected]

Accepted 12 August, 2016

The dermis of skin where all the activities concerning leather processing take place, has been scantily attended to, especially in the camel skin (hide). Histological studies of this skin region in the camel revealed fine collagenous structures in the upper layer laced with numerous elastic fibers. Below this layer, actually touching each other is a layer of interconnecting small sheets in form of slabs of collagen. The layer, together with a lower layer of larger slabs of almost vertical fibers of collagen, forms the corium proper. These layers are more prominent in the wet blue (early form of leather after tannins have been infused – before final finish). The trio groups of secondary and primary hair follicles do not penetrate too far down into the corium but eventually leave some voids that give the grain (upper part of the leather), a similar appearance to that of goat. Ironically, the skin (hide) of the camel is not as thick as that of Nigerian cattle, and the ratio of the thickness of the camel’s raw stock papillary layer to the corium (upper and lower) is 22.86%, while that of the uppermost part of the wet blue is 24.04% which means that after the epidermis and hairs have been removed, the ratio becomes higher. The removal of blood vessels and nerves during bating (enzyme used to remove unwanted materials) pushed the corium apart and increased the ratio in wet blue. Because camel leather is not as thick as that of cattle, it may not yield a relatively thick enough grain split and/or, flesh split leather. Key words: Epidermis, dermis, grain, corium, wet blue.

INTRODUCTION The camel, being a desert animal poses environmental problems, especially as they relate to adaptation. Its outermost structure, the skin (hide for large animals in leather parlance), presents many challenges for investigation because of its incongruous build. Apart from a general information about the animal (McKnight, 1969), many studies on the histological structure of its skin have been carried out. These range from the normal structure (Jarrar and Faye, 2015; Lee and Schmidt-Nielsen, 1962; Dowling and Nay, 1962; Gbolagunte, 1983), to those on leather (Gbolagunte and Jamdar, 1984; Hekal, 2014) and the ones referring to adaptation to the environment (Gbolagunte, 2016a, b). However, none mentioned the nature of the dermal structure as it determines the type of leather made from it.

Dermal fibers, especially the collagen fibers make up leather. The physical and chemical properties of the various types of leather are decided by the inherent characteristics and arrangements of the fibers within the

dermis and also, by the degree to which these fibrous components can be altered during the penetration of materials into the hides or skins.

The histological structure of the skin of the camel, is basically similar to those of other domestic animals (Lee and Schmidt–Nielsen, 1962) except in the arrangement of hair follicles (Gbolagunte, 1983; Gbolagunte and Jamdar, 1984; Hekal, 2014). This similarity mainly concerns the general morphology; but the basic variation in characters, like the specific nature of the grain (area immediately below the epidermis) surface, in relation to the corium (lower dermis); the types of fibers found within the various layers and positions, and in the nature of weave of the fibers therein; all of which can influence the properties of the resultant leathers, have not been effectively established.

General advantages like the number of splits, sponginess of the leather and the feel of the grain surface have been attributed to parameters like thickness of the

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168 J. Sci. Res. Stud. hide or skin (Gbolagunte and Jamdar, 1984), the void spaces created as a result of the removal of some skin appendages like the hair follicles and glands (Mellon et al., 1963) and the actual dimension of the papillary layer itself (Everett and Hannigan, 1978).

This study is directed at establishing, histologically, the nature of the grain layer of the camel in contrast to the corium, with emphasis on the type of fibers therein and the relationship between them. It is also intended to note the effect of tanning on the microscopic structure of the wet blue (early stage of tanning after tannins – chrome, have been added to fix the fibers before finishing with dyes), and, to finally determine the percentage ratio of the thickness of the grain layer of this animal’s skin to the corium, in both the raw stock and wet blue. MATERIALS AND METHODS Materials Skin samples of raw camel hides obtained from the abattoir were immediately fixed in 10% buffered formal saline solution. More samples of raw and wet blue chrome – tanned hides that were sent from the Great Northern Tanning Company (GNT) in Kano, Nigeria were studied. They were wrapped in cellophane papers. As soon as the samples were received, they were fixed likewise.

Histological study The fixed samples were dehydrated in various grades of alcohol, cleared in benzene, and wax – impregnated using a Histokinette Tissue Processor. The tissues were embedded in paraffin. Vertical and horizontal sections were cut serially at eight microns with a rotary microtome. They were variously stained with routine haematoxylin and eosin; Mason’s Trichrome; Phosphotungstic acid Hematoxylin (PTAH) and some others, with silver stain (Luna, 1968).

The thickness of the grain of the raw samples was determined by the depth of the hair follicles that had contact with the skin surface; therefore, the average hair follicle depth and the average thicknesses of the whole dermis were used to determine the thickness of the grain and corium and, the percentage ratio between the two. In short, the average hair follicle depth was subtracted from the average thickness of the whole dermis to obtain the average thicknesses of the grain and corium separately.

Leather assessment studies

Skin tannage

Whole skins were subjected to tannage into wet blue

leathers using chromium oxide (chrome) according to the standard mineral tanning methods (Tuck, 1981). The tanned skins were thus converted into non-putrescible materials after which histological studies were carried out on them. In the wet blue, the appearance of the fibers in the two layers was the differentiating factor.

RESULTS

The Grain layer

The Raw stock

The grain layer of the raw skin section of the camel was observed to be that portion extending from below the basal cells of the epidermis, to the tip end of the hair follicle group which had contact with the skin surface. Just below the epidermis, very close-knit, tightly interwoven fibers were observed. These fibers were thinner than collagen fibers; wavy and highly branched (Figure 1); below this layer were small slabs of still tightly-woven collagen fibers, with very short lengths, so short that weave pattern could not be ascertained precisely. These small collagen fibers were still regularly interconnected with elastic fibers.

Around the hair follicles, actually embedding them, the fibers appeared very similar to those just below the epidermis, but much finer; in actual fact, threadlike, while those below the epidermis lay parallel to the surface of the skin, those around the hair follicles were vertical, like a bunch of hanging threads (Figure 2).

The presence of abundant ground substance around the fibers which embedded the hair follicles categorized them as delicate collagenic fibers, looking reticular.

Wet blue

The wet blue grain layer clearly showed a distinct zone of parallel elastic fibers which existed directly below the epidermis of the raw stock. In the wet blue, the section had no epidermis which had already been removed during liming. The portion where the short slabs of collagen fibers were found in the raw stock, now appeared like a layer of parallel fibers in the skin surface with numerous interweaving meshes of elastic-like fibers (Figure 3).

The thread-like appearance of the fibers embedding and, also forming septae around the hair follicles became quite apparent; demarcating the periphery of the voids that remained after the hair follicles had been removed at liming. There was a distinguishable difference in the appearance of the grain layer from the upper corium of the wet blue, even though both appeared to be well merged.

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Figure 1. Raw stock with close – knit tightly interwoven fibers. They are very thin, flexible and wavy. Note the small slabs of collagen fibers with short lengths below (arrows). H&E × 120.

Figure 2. Raw stock like hanging threads around the hair follicle (arrows), which are delicate collagenic fibers. PTAH × 400.

Figure 3. Wet blue grain layer with the parallel elastic fibers which were below epidermis of the raw stock. Note the numerous interweaving meshes of elastic – like fibers. PATH 600.

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Figure 4. Raw stock upper corium. Note the vertically oriented, high angled, low – weave of moderately long slabs of collagen bundles. Note short slabs of collagen bundles between the long slabs. H&E 120.

Figure 5. Wet blue of the lower corium. Collagen fibers are of medium weak weave. Note that the slabs are not usually very long as those in the upper corium. PTAH 600.

The corium An upper zone of vertically oriented, high angled, low weave, moderately long slabs of collagen bundles, which can rightly be referred to as the “upper corium” was observed in both the raw stock and the wet blue of the camel hide. In between the partial weave of these long slabs of collagen bundles were the short slabs of maturing collagen bundles similar to those found below the elastic fiber zone in the grain layer (Figure 4).

In the lower corium of both the raw stock and wet blue, the collagen fibers were of medium weave, while the slabs of the bundles were not usually very long as those in the upper corium (Figure 5).

The main characteristics in the nature of the corium of the raw hide and wet blue were found in the appearance of the various dermal constituents other than collagen fibers, while the hair follicles and sweat gland secretory portions were observed in the sections of the raw hide, their voids could only be seen in those of the wet blue. Moreover, the wet blue fibers appeared more compact than those of the raw hide.

In the hypodermis or the subcutaneous layers of both the raw stock and wet blue, were very thin, loosely interweaving reticular fibers with abundant ground substance. This layer, rich in nerves and blood vessels (Figures 6 and 7) structures were mostly observed in the sections of the raw hide. This layer was to a large extent

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Figure 6. Hypodermis of Raw stock. Note blood vessels in form of arterio–venous anastomoses. H&E 400.

Figure 7. Raw stock hypodermis. Note the prominent nerve structure (arrow). PTAH × 600.

Table 1. Average thicknesses of the dermal layers of the raw stock and wet blue of the camel hide in millimeters.

Layers Raw stock (mm) Wet blue (mm)

Papillary 0.75 0.50

Upper corium 1.70 1.00

Lower corium 0.83 0.58

Hypodermis 0.70 0.83

Average 3.98 2.91

devoid of fat cells. Percentage ratio of the thickness of grain to corium The total thicknesses of the various dermal layers in the raw camel hide and its wet blue were 3.98 and 2.91 mm respectively (Table 1). The percentage ratios of the thickness of the papillary layer to the corium (minus the hypodermis) in both raw stock and wet blue were 22.86

and 24.04% respectively (Table 2). DISCUSSION Because the grain merges well with the corium in the skin section of the camel, the suspicion, for some time now, that there is no distinguishable demarcation between the grain and the corium in the camel hide is somehow justified with this study. The structure of the fibers in the

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Table 2. Percentage ratio of grain to corium in the raw stock and wet blue of camel hide.

Layers Raw stock (mm) Wet blue (mm)

Papillary layer 0.75 0.50

Corium (Upper and lower) 2.53 1.58

Ratio 1:3.4 (22.86%) 1:3.2 (24.04%)

grain is, however, definitely distinct and could be seen as far as the depth of the hair follicles that have contact with the skin surface.

The natural grain tightness (the natural tension of the grain layer) and the merging of the grain into the corium (the attachment of grain to corium) play the guiding role in their production of tight grained leather with fine break. The more pronounced of the two conditions overruns the effect of the other conditions (Das et al., 1968). Hence, whatever may be the degree of grain tightness in this animal’s skin, the good merging of the grain to the corium in both the raw stock and wet blue, indicate that this hide should exhibit a leather with tight grain and fine break.

Since compact packing of collagen fibers may be reasonably assumed to have some influence on the tightness of the grain (Das et al., 1968), the vertical orientation and the high angle of weave of the fibers in the corium in both the raw stock and wet blue however, suggests the tendency for a possible loose grain in the leather of this animal’s hide. It could also be a factor of its genetic makeup (Duffy et al., 1983; Peters and Duffy, 1985) or even the season (Roddy, 1956). The observation here that the wet blue corium’s fibers appeared (under the microscope) more compact than the raw stock, implies that some tightness may have been imparted to the grain in wet blue, most probably because of the “filling action” during tannage.

The characteristic grain appearance of the camel leather, with its fine grain looking like that of a goat skin leather, is a function of the fundamental trio group arrangement of the compound hair follicles (Gbolagunte, 1983; Gbolagunte and Jamdar, 1984), seen as voids in the wet blue.

Those threadlike fibers that embed the hair follicles in the raw stock and also demarcate the hair follicle voids in the wet blue, which were also identified as reticular fibers, should enhance the ultimate distension of the camel hides’ grain; reticular fibers are, actually, supporting fibers (Dodd, 1979).

It should nevertheless be expected that those hair follicles and their subsequent wet blue voids in the grain could affect the penetration of the materials into the hide and leather, and also affect the degree to which the fibrous component can be altered and rearranged to make leather of different properties. Earlier studies in the cattle however, have confirmed that the removal of these structures produces void spaces of from 4 to 15% of the total volume in the various layers of the grain, though

other layers of the dermis also have void spaces, those in the grain must be greater than 50% of the total volume (Mellon et al., 1963). Moreover, since the grain fibers are much smaller than those of the corium, they should, even after all the materials in the hide have been removed act as very fine filters compared with the coarse fibers which would act as coarse filters. A slower transfer of materials through the grain of the hide rather than through the corium of the hide is expected in this regard.

The frequency with which the corium fibers interweave is the overriding factor in the strength of leathers whose natural weave of fibers can be tampered with by splitting. Usually, high angle of weave and smaller depth of corium (especially if part of it has been split along with the grain, for a thick grain split), results in a weak leather (Haines, 1981). It is therefore expected that the upper corium of the camel hide with its vertical high angle of weave of the fibers being less compact and less interwoven, will offer less support to the grain during shoe lasting; whereas, a flesh split that consists of the lower corium, with its medium weave (relatively greater frequency of weave than the upper corium), will have adequate strength - especially since this lower corium fibers are anchored by flatly running flesh layers.

Differences in structure, often arise from differences between original raw hides and very dependent on hide thickness (Haines, 1981). The 3.98 mm thickness of the raw stock and the 2.91 mm thickness of the wet blue, indicate that the dermis of the camel is thinner than that of European cattle, whose average thickness is 6 mm, and still thinner than those of the White Fulani 4.90 mm, N’ Dama 4.76 mm and Muturu, 4.20 mm (Amakiri, 1975). The papillary layer (grain) reflects a similar trend. Conclusion The characteristics of the dermal structures of the raw stock and wet blue (leather after tanning with chromium), revealed that overall, it is established here that there is a distinct grain which merges well with the corium of the camel hide, and that the manner of contact between the two layers indicate a tendency toward an ultimate tight grain and fine break especially due to the filling action during tannage, with the grain fibers acting as fine filters. In addition, the grain split of the camel hide’s leather should be weaker in strength than the flesh split for reasons of the nature of fiber weave and anchor. The

hide of the camel, is not as thick as that of cattle and so, may not yield such a considerable amount of split as the latter. Acknowledgements I sincerely acknowledge the interest of the Vice Chancellor of Crawford University for seeing that I disseminate all my findings concerning my research into the camel skin to the world. I am also grateful to Mr. J.K. Oyinloye’s tremendous effort in the preparation of the histological slides in this study. REFERENCES Amakiri SF (1975). The skin structure of some cattle breeds in Nigeria

studied in relation to hide productions. J. Niger. Vet. Med. Assoc. 4(1):21-28.

Das DK, Sarkar KT, Mitra SK (1968). In: Bhaskaran R, Nandy SC, Krishna mirthi VS (eds.) Proc. Seminar of Central Leather Research Institute, Council of Scientific, and Industrial Research, CLRI, Adyer, Madras. p. 141.

Dodd EE (1979). In: Atlas Of Histology “(Mcnow, Alice And De Leo, Henry C.) McGraw Hill; San Francisco; p. 31.

Dowling DF, Nay T (1962). Hair follicles and sweat glands of the Camel (Camelus dromedarius). Nature London, 195:578-580

Duffy JH, Peters DE, Bavinton JH (1983). Studies of the cause of the vertical fiber hide structure in Hereford cattle. J. Soc. Leather Technol. Chem. 64(3):70-73.

Everett AL, Hannigan MV (1978). The vertical fiber hide defect: transmission to progeny and relation to reproductive failures in cross breeding pest. J. Am. Leather Chem. Assoc. 73:458.

Gbolagunte GD (1983). Micro anatomical studies of the skin of the one humped camel (Camelus dromedanrius) with particular reference to the hair foillcles and sweat glands measurements. M.sc Thesis. Ahmadu Bello University, Zaria, Nigeria p. 154 URL:http/hdl. handle .nett/123456789/5337.

Gbolagunte 173 Gbolagunte GD (2016b). Reclassification of the sweet glands of the

one-humped camel (Camelus dromedrious) as apocrine based on mode of secretion and extrusion. Am. J. Res. Commun. 4(5):151-170.

Gbolagunte GD, Jamdar MN (1984). Histology of the camel (Camelus dromedarius) hide in relation to leather manufacture. J. Leather Res. 2(1):1-9.

Gbologunte GD (2016a). Fibrocartilage embedding hair follicles on the camel (Camelus dromedrious): An ideal structure for its comfort. J. Sci. Res. Stud. 3(2):30-33.

Haines BM (1981). In: Fiber Structure of Leather. Leather Conservation Center, North Hampton, p. 24.

Hekal S (2014). Histological study of the skin and leather characteristics in two types of Arabian camels (Camelus dromedarius). J. Am. Sci. 10 (9):41-47.

Jarrar MB Faye B (2015). Normal pattern of camel histology. Food and Agriculture Organization of the United Nations and Ministry of Agriculture. Kingdom of Saudi Arabia.UTF/SAU/021. p.162.

Lee GD, Schmidt-Nielsen K (1962). The skin, sweat glands and hair follicles of the camel (Camelus dromedarius). Anat. Rec. 143:71-77.

Luna LG (1968). In: Manual of histologic staining methods of the armed forces Institute of Pathology, Mcgraw Hill Book Company, New York, p. 258Luna LG (Ed.) Third Edition.

Mcknight TL (1969). The Camel in Australia. Melbourne University Press.

Mellon EF, Audsley MC, Viola SJ, Naghski J (1963). The contribution of hair follicles and sebaceous glands to the void space of hides. J. Am. Leather Chem. Assoc. (JALCA), 58(9):514.

Peters DE, Duffy JH (1985). The effectiveness of selective breeding for reducing the incidence of the vertical fiber hide condition in Hereford cattle. J. Am. Leather Chem. Assoc. (Jalca), 80:42-46.

Roddy WT (1956). Structural characteristics of cattle hides and skins: Prepared by Education Committee National Hide Association. (Minnock John K ed.) Distributed by Jacobsen publishing Co. Chicago, Illinois pp. 6-11.

Tuck DH (1981). In: The Manufacture of Upper Leathers. Tropical Products Institute, London, UK, pp. 34-59.