540 COMPARATIVE. HISTORICAL. 



Under such circumstances, absorption, as of potassium iodid, may take 

 place from ointments. Thus, v. Voit observed globules of mercury be- 

 tween the layers of epidermis and even in the corium of an executed in- 

 dividual, to whom, while still warm, he had given vigorous inunctions. 



In courses of treatment with inunctions of mercurial ointment, globules of 

 mercury penetrate, on rubbing, also into the hair-follicles and excretory ducts of 

 the glands, where under the influence of the glandular secretion they may be 

 transformed into a combination susceptible of absorption. In addition, mercury, 

 in the form of vapor, reaches the respiratory mucous membrane, where, likewise, 

 it is transformed into an absorbable combination. The inflamed skin, especially, 

 however, when covered with fissured or injured epidermis, absorbs rapidly, like 

 a wound-surface. As all substances that irritate the skin sever the continuity of 

 the latter when the effect is long continued, it can readily be understood that 

 they are eventually absorbed from the wounded areas. 



As the skin, under normal conditions, absorbs oxygen from the 

 atmosphere, it may also absorb gases, such as hydrocyanic acid, hydro- 

 gen sulphid, carbon monoxid, carbon dioxid, vapors of ether and chloro- 

 form. From a bath that contains absorbed hydrogen sulphid, this gas 

 is absorbed; conversely, carbon dioxid is given off to the bath-water. 



In frogs, active absorption of watery solutions takes place through the skin, 

 the epidermal cells undergoing enlargement and exhibiting motor phenomena. 

 These phenomena may also be induced artificially by electric stimulation. The 

 frog also absorbs much water through the skin even when the circulation is elimi- 

 nated and the central nervous system is destroyed; though more, however, when 

 the circulation is maintained. The skin of the frog exhibits, in the process of 

 absorption, a vital cellular activity, in consequence of which penetration takes 

 place from without inward. 



The transfer of watery solutions through the skin by means of the constant 

 galvanic current, cataphoric action, is a matter of especial interest. Both elec- 

 trodes are impregnated with a watery solution of the substance in question, and 

 the direction of the current is altered from time to time. Thus, H. Munk was 

 able to introduce through the skin of rabbits within several minutes strychnin, 

 from the effects of which they died. In man, the introduction of quinin and po- 

 tassium iodid into the body was thus effected, these substances being subsequently 

 demonstrated in the urine. In the introduction, the compound bodies are 

 (always?) decomposed by the current; thus, for instance, the positive pole of the 

 current introduces the calcium of calcium chlorid; the negative, only chlorin. 



COMPARATIVE. HISTORICAL. 



In all vertebrates, the skin consists of corium and epidermis. In reptiles, 

 the cornification of the epidermis occurs in large plates (scales of the snake, 

 shell of the tortoise). Among mammals, the armadillo exhibits a similar forma- 

 tion. In addition to hair and nails, there occur in animals, as epidermoidal struc- 

 tures, prickles, bristles, feathers, claws, hoofs, horns (the antlers of the. deer are 

 bony formations arising from the frontal bone) , spurs (cock) , the horny covering 

 of the beak of turtles and of birds, and the horn of the rhinoceros. The scales of 

 fish, on the other hand, consist of ossified portions of skin. Some fish possess 

 considerable portions of bone upon the skin. 



The skin is provided with a large variety of glands. In the amphibia, they 

 secrete either mucus alone or poisonous substances. Serpents and tortoises possess 

 no cutaneous glands at all. In lizards, the thigh-glands extend from the anus to 

 the popliteal spaces. In crocodiles the glands open beneath the margin of the 

 cutaneous osseous scales. Birds have no cutaneous glands. The coccygeal gland, 

 situated above the coccygeal vertebra, furnishes a secretion for lubricating the 

 feathers. 



The civet-glands at the anus of the civet-cat, the preputial glands on the 

 musk-bag of the musk-deer, the inguinal glands of the hare, the pedal glands of 

 ruminants are peculiarly developed sebaceous glands. The strongly odorous 

 castoreum is the secretion of the prepuce in both sexes of the beaver. 



