Further study of the relationship between blood and lipids has permitted the recognition of several peculiarities concerning the blood serum which when related to abnormal conditions, acquires a special significance. Policard has observed that when crystals of cholesterol are added to blood sera, two opposite changes can ensue. In one, a precipitate appears while the serum cholesterol content decreases. On the contrary in the other, a part of the added cholesterol passes in solution into the serum, thereby causing an increase in cholesterol content. When animals were treated with large amounts of sterols for a long time, their sera showed this tendency to precipitation when in contact with cholesterol in vitro, while the sera of animals treated with large amounts of fatty acids showed the capacity of dissolving more cholesterol. We believe that this capacity of sera to precipitate in the presence of cholesterol may be correlated with the clinical conditions present in arteriosclerosis when acute episodes occur.

Table XXXIII. Effect Of Lipids Administered In Vivo Upon The Total Number Of Leucocytes

These studies of the role of lipids in blood physiology suggest that the general antagonism between sterols and polyunsaturated fatty acids also intervenes in other important processes of blood physiology. It has thus raised the question of the role these lipids may play, through their opposite effects, in different metabolic balances of the body governed by blood changes.