790 THE SKIN AND ITS SECRETIONS. 



pages 112, 113 and in this connection it must be mentioned that, accord- 

 ing to the investigations of RUTHERFORD and HAWK/ the sulphur content 

 of human hair is higher in men than in women, at least for the Caucasian 

 race, and also that red hair has the highest sulphur content irrespective 

 of race or gender. Hair on incineration leaves considerable ash, which 

 in human hair varies between 2.6 and 16 p. m., and in animal hair 

 is still greater, even up to 71 p. m. in the hair of the deer. The ash 

 consists of large amounts of alkali and calcium sulphate, and its sulphur 

 probably originates from the organic substance, which make the state- 

 ments as to the composition of the ash of hair of little value. Calcium 

 occurs in larger amounts, especially phosphate as well as carbonate, and is 

 most abundant in white hair. The amount of iron oxide in 1000 grams 

 of the ash of human hair varies between 42.2 grams in blond and 108.7 

 grams in brown hair, and silicic acid between 66.1 grams in black and 

 424.6 grams in red hair (BAUDRIMONT) . The nails are rich in calcium 

 phosphate and the feathers rich in silicic acid, especially the feathers 

 of grain-eating birds. According to v. GORUP-BESANEZ 2 the quantity 

 of silicic acid in grain-eating birds was 400 p. m., and in meat, berries 

 and insect-eating birds the amount was only 270 p. m. of the total ash. 

 DRECHSEL 3 claims that at least a part of the silicic acid exists in the 

 feathers in organic combination as an ester. 



According to GAUTIER and BERTRAND 4 arsenic also occurs in the 

 epidermal formations. GAUTIER says that arsenic is of importance in 

 the formation and growth of the formations, and on the other hand the 

 hair, nails, and epidermis-cells, are of great importance in the excretion 

 of arsenic. 



The skin of invertebrates has been the subject, in a few cases, of 

 chemical investigation, and in these animals various substances have 

 been found, of which a few, though little studied, are worth discussing. 

 Among them tunicin, which is found especially in the mantle of the 

 tunicata, and the widely diffused chitin, found in the cuticle-formation of 

 invertebrates, are of interest. 



Tunicin. Cellulose seems, from the investigations of AMBRONN, to occur 

 rather extensively in the animal kingdom in the arthropoda and the mollusks. 

 It has been known for a long time as the mantle of the tunicata, and this animal 

 cellulose was called tunicin by BERTHELOT. According to the investigations 

 of WINTERSTEIN there does not. seem to exist any marked difference between 

 tunicin and ordinary vegetable cellulose. On boiling with dilute acid, tunicin 

 yields dextrose, as shown first by FRANCHIMONT 5 and later confirmed by WIN- 



TERSTEIN. 



1 Journ. of Biol. Chem., 3. 



2 Lehr. d. physiol. Chem., 4. Aufl., 660, 661; Baudrimont, ibid. 



3 Centralbl. f. Physiol., 11, 361. 



4 Gautier, Compt. rend., 129, 130, 131; Bertrand, ibid., 134. 



5 Ambronn, Maly's Jahresber., 20; Berthelot, Annal. de Chim. et Phys., 56, Compt. 



