530 PRINCIPLES OF VETERINARY SURGERY 



otic animals, as the number of red blood cells diminish by 

 one-fourth. The presence of melanotic gi-anules in the blood 

 of melanic horses does not prove that the pigment is formed 

 there and afterwards deposits itself in the tissues. The 

 granules are rather carried into the blood by the leucocytes, 

 which have brought them from without. 



It is known today that the pigment is contained in the 

 proper cells of the tissues, that the melanotic granules have 

 no proper organization, and lastly that the blood that has 

 flowed out undergoes different transformations. It must 

 logically be admitted that melanin is produced like all other 

 pigments, in a word, that it is the result of cellular activity. 

 The data we possess on the general physiology of pigments 

 shows that they are elaborated by special cells of mesoblastic 

 origin, that the pigments are formed by the cellular proto- 

 plasm, and that they accumulate in the latter without en- 

 croaching on the nucleus. The behavior of these pigmentary 

 cells on the lower vertebrata (toads) has been closely 

 studied. The studies have shown that they are cells of 

 mesoblastic origin, ramifying and migratory, which form 

 pigmentary granules and which perform the function of 

 transporting them into the midst of the epidermic cells, 

 which in turn incorporate the pigment. In the case of high- 

 ly pigmented mammals, for example, the gorilla, it has been 

 proven that there are ramifying pigmentary cells in the sup- 

 erficial cells of the derma, which send extensions among the 

 elements of the malpighian bodies to which they give up 

 their granules. The same phenomena occurs in the negro. 

 A layer of starry pigmentary cells, forming plexuses be- 

 tween the dermis and epidermis, is found in the horse and 

 the ass, proving that there are cells the function of which is 

 to elaborate the pigment. In short, melanin is elaborated 

 by certain cells and conveyed into the tissues by them or by 

 the blood. It remains to determine the mechanism that gov- 



