22 TATTY DEGENERATION. 



now suspended, the oily detritus, has its physiological prototype 

 in the secretion of the mammary gland ; the more uniform dis- 

 tribution of the refracting particles giving it a whiter, or even 

 absolutely white, colour, just as in emulsions which have been 

 artificially prepared. 



§ 29. If we inject milk into the abdominal cavity of a 

 rabbit it disappears very quickly ; it is still more rapidly ab- 

 sorbed from the subcutaneous areolar tissue. Milk, therefore, 

 and consequently all fatty dehins, are capable of being absorbed, 

 and are usually absorbed, unless absorption is prevented by some 

 exceptional conditions. One of these deserves especial notice, 

 viz. when the products of fatty degeneration are enclosed in a 

 cavity whose walls are in a state of inflammatory irritation, and 

 consequently inclined rather for productive than for absorbent 

 activity. Those products have, under such circumstances, to 

 undergo a farther series of changes. The fatty matters are 

 partly saponified, partly deposited in those solid forms with 

 which we became acquainted during our study of necrosis. 

 Finally, an abundant deposit of cholesterin crystals takes place ; 

 these give the dirty-white mass (whose consistency, according to 

 the amount of fluid present, may be either friable or pulpy) a 

 peculiar lustre (atheromatous pulp — atherombrei — griitzbrei). 



Cholesterin, which we now meet with for the first, though 

 not for the last, time, is still, notwithstanding numerous investi- 

 gations, a very enigmatical substance. 



Its presence in the brain and spinal cord, under perfectly 

 normal conditions, in enormous quantity (40 parts in 1,000) 

 does not allow us to dismiss it summarily as an excrementitious 

 substance. Its constant presence in the biliaiy secretion is 

 readily accounted for by the fact that the bile is one of the few 

 fluids which is capable of holding it in solution. Chemistry 

 informs us that, besides the bile, it is only solutions of soap and 

 fatty oils which can dissolve it, and these only to a limited 

 extent. 



This high degree of insolubility in animal fluids is one of 

 the most striking properties of cholesterin ; it is the cause of 

 our so often meeting with it in a solid state. 



The regular crystalline form which it assumes is that of a 

 rhombic plate, whose angles are uniformly =79" 30' and 100" 30'. 

 These plates tend to form aggregates with their longer sides 



