Fig. 8. 



88 PKOXIMATE PRINCIPLES OF THE SECOND CLASS. 



These substances crystallize in very slender needles, which are 

 sometimes straight, but more often somewhat curved or wavy in 

 their outline. (Fig. 7.) 



They are always deposited in a more or less radiated form ; and 

 have sometimes a very elegant, branched, or arborescent arrange- 

 ment. 



When in a fluid state, the fatty substances present themselves 



under the form of drops or 

 globules, which vary indefi- 

 nitely in size, but which 

 may be readily recognized 

 by their optical properties. 

 They are circular in shape, 

 and have a faint amber color, 

 distinct in the larger globules, 

 less so in. the smaller. They 

 have a sharp, well defined 

 outline (Fig. 8) ; and as they 

 refract the light strongly, 

 and act therefore as double 

 convex lenses, they present 

 a brilliant centre, surrounded 



OLEAGINOUS PRINCIPLES F HUMAN FAT. , , , , . 



Stearine and Margarine crystallized ; Oleiiie fluid. DJ a QarK border. 



marks will generally be 

 sufficient to distinguish them under the microscope. 



The following list shows the percentage of oily matter present in 

 various kinds of animal and vegetable food. 1 



QUANTITY OF FAT ix 100 PARTS IN 



Filberts . 

 Walnuts 

 Cocoa-nuts 

 Olives . 

 Linseed 

 Indian Corn 

 Yolk of eggs 



60.00 

 50.00 

 47.00 

 32.00 

 22.00 

 9.00 

 28.00 



Ordinary meat 

 Liver of the ox 

 Cow's milk 

 Human milk 

 Asses' milk . 

 Goats' milk . 



14.30 

 3.89 

 3.13 

 3.55 

 0.11 

 3.32 



The oleaginous matters present a striking peculiarity as to the 

 form under which they exist in the animal body; a peculiarity 

 which distinguishes them from all the other proximate principles. 

 The rest of the proximate principles are all intimately associated 

 together by molecular union, so as to form either clear solutions or 



1 Pereira, op. cit., p. 81. 



