PRINCIPLES OF VETERINARY SURGERY 529 



pathological as in the normal state. The former is but an 

 excessive activity of the hyperplasia of the pigmentary cells. 

 But it is not always easy to distinguish the normal state, be- 

 cause some animals possess a special aptitude for the accumu- 

 lation of pig-ments in the connective tissue cells. The calf, 

 in particular, sometimes exhibits a- marked pigmentation of 

 the connective tissue cells of the endothelium of the perito- 

 neum, the meninges, and the connective tissue surrounding 

 the nerves, etc. In the ox there is frequently found a slate 

 colored pia mater over the frontal lobes, which on micro- 

 scopic examination proves to be a simple superpigmentation, 

 analogous to that seen in toads and fishes, with the excep- 

 tion that there is no cellular proliferation. The slight differ- 

 ence between the physiological and pathological states at 

 commencement is difhtult to comprehend. 



It has, therefore, been wrongly claimed that the melan- 

 otic pigment is farmed in the blood. The blood, and espec- 

 ially its coloring, must furnish the cells with materials for 

 their elaboration. Ehrman has seen the pigment form at 

 the expense of extravasated blood, and in following the de- 

 velopment of amphibians with unpigmented eggs (salaman- 

 ders) he has clearly seen the pigment develop, but only after 

 the development of the blood vessels. Other facts support 

 this view. Pouchet has demonstrated that in pouring blood 

 into an alcoholic solution of bichloride, a precipitate of black 

 pigment is obtained that has all the appearances and prop- 

 erties of the choroid pigments, the melanotic pigments, etc. 

 This artificial pigment occurs in the form of lozenge-shaped 

 bodies of crystalline aspect, or rather of spherical or irregu- 

 lar masses (i to 40 microns). It has the chemical reaction 

 of melanin. This experiment demonstrates the possible 

 transformation of the coloring matter of the blood into mel- 

 anin. Brandt and Pfeiffer have always claimed that there 

 is an impoverishment of the blood in haemoglobin in melan- 



