500 



TEGUMENTARY ORGANS. 



Simple coecal glands are scattered over the 

 whole surface of the body of the Procession 

 Caterpillars, opening at the points of the hairs ; 

 on the sides of the body in Myriapods. on the 

 joints of the legs in Beetles and Bugs. 



In Mollusca a peculiar, probably glandular, 

 canal exists in the foot of certain Lamelli- 

 branchs, and glandular coeca have been ob- 

 served in the lower surface of the foot in 

 Paludina. A ciliated canal runs in the foot 

 of Pulmonata, and receives glands on each 

 side. The existence of cutaneous glands in 

 the Cephalopods appears doubtful at least, 

 H. Miiller could only find them as shell 

 glands in the expanded arms of Argonauta. 



Among the Vertebrata, Fishes, Ophidia, 

 Chelonia and Birds, appear to possess no 

 proper cutaneous glands * ; in Sauria they 

 attain a very slight and local, but in 

 Batrachia and Mammalia, an immense de- 

 velopment. In the frog, the whole surface 



Fig. 318. 



The cutaneous glands of the Frog. 

 A, section ; B, superficial view. 



of the ecderon is beset with minute trifid 

 apertures, so disposed between three epi- 

 dermic cells, as to present a singular resem- 

 blance to the stomata of plants (Jig. 318. B). 

 These lead directly into spherical sacs (fig. 

 318. A. d.), which are lined by a continuation of 

 the cellular ecderon, and lie in the superficial 



* Dr. Clark, in his excellent account of the skin 

 of the eel (Trans. Mic. Soc. 1849), describes cuta- 

 neous glands in that animal. The so-called " glands " 

 of the lateral line, however, have since been shown 

 by Leydig to have a very different structure ; and 

 I confess I have not been able to convince myself of 

 the existence of the other glands described'by Dr. 

 Clark. I can find nothing like them, except the 

 strong perpendicular semi-elastic bands, which tra- 

 verse and unite the bundles of connective tissue in 

 this as in other fishes. 



part of the enderon above its stratified layer 

 (Jig. 318. A. g.) (vide infra). Nerves (/) 

 and vessels penetrate the latter to reach the 

 superficial layer of the enderon, and ramify 

 among these close-set glandular sacs. The 

 sacs usually contain only a clear fluid * ; they 

 are contractile, and may be made to expel 

 their contents by irritation of the nerves dis- 

 tributed to them.f 



In Mammals, we meet with two kinds of 

 cutaneous glands, sebaceous and sudoriparous. 

 The former are almost invariably developed 

 in connection with the hair sacs, consisting 

 in fact of diverticula of the Malpighian layer 

 of the cellular ecderon of the upper portion 

 of these sacs, whence their position is always 

 superficial. The innermost cells of the solid 

 process become filled with fat break down, 

 and pour their contents into the hair sac 

 itself, by whose aperture they make their exit. 

 Sometimes, as in the hairs of the head in man 

 and in the pig's bristles, the sebaceous glands 

 are very small and simple, while in other lo- 

 calities they throw out processes, and assume 

 the appearance of complex racemose glands, 

 disposed like rosettes around the hair-sac, 

 from which they are developed. 



Sudoriparous glands. These glands, like 

 those just described, are, as Gurlt pointed out, 

 simple, elongated processes of the deep layer 

 of the ecderon, differing from the sebaceous 

 glands chiefly in producing a clear fluid, instead 

 of a fatty secretion. As Kolliker has shown, 

 however, no line of demarcation is to be drawn 

 on this ground, the secretion of the axillary 

 sudoriparous glands in man being an essentially 

 sebaceous substance. The sudoriparous glands 

 are cylindrical coecal tubes varying, in man, from 

 TOO to -s&o f an mcn m diameter, whose walls 

 are either thick or thin. In the former case 

 they consist of a simple ecderonic cellular coat, 

 contained within a prolonged sheath, formed by 

 the uppermost layer of the enderon, and, like 

 it, composed of a homogeneous or indistinctly 

 fibrillated periplast, with imbedded endoplasts. 

 Outside this, or rather forming part of it, is a 

 layer of longitudinally-disposed smooth mus- 

 cles, and the whole is coated, like the deep sur- 

 face of the rest of the enderon, by a more or 

 less distinct layer of connective tissue. In 

 the thin-coated glands the muscular layer is 

 absent, but the cellular ecderonic coat is fre- 

 quently so thick that they possess no cavity at 

 all. The thick-walled glands are met with in 

 man in the axilla, scrotum, anal region, &c. ; 

 while those of the rest of the body are al- 

 most entirely of the thin- walled description. 

 The glands terminate superiorly in undu- 

 lating canals, which reach the surface of the 

 enderon, and are continued to that of the 

 ecderon by oblique channels excavated in its 

 substance between its cells. Inferiorly, they 

 form close coils, which lie in the subcutaneous 



* Stated by Bergmann and Leuckart to have an 

 irritating property in Triton. 



t Ascherson : *Haut-driisen d. Frosche, Miiller's 

 Arrhiv, 1841. Czermak : Haut-nerven d. Frosche 

 Ibid. 1849. 



