THE GENERAL CONSTITUTION OF LIVING BEINGS. 87 
ing death, have been restored to life by the transfusion of 
blood from a being of the same species of either sex; we 
know, moreover, that calves’ blood and lambs’ blood have 
been injected into the veins of men who have lived after it; 
that.the case has been the same in the instance of the 
transfusion of human blood into a dog, of that from a sheep 
and a calf into a dog, from a calf to a sheep and a chamois, 
and in the case of transfusion from a dog,a rabbit, or a 
Guinea-pig, to a hen and a cock. These phenomena of 
physiology, added to the results of anatomical observations, 
leave no doubt as to the specific identity of the elements 
in the entire animal series. 
This acknowledged identity in the solids extends also 
to the liquids of the living system, and these liquids are 
parts not less indispensable for the complete effect of vital 
phenomena. Formed by the mixture of very many imme- 
diate principles dissolved by each other’s help in water, 
and holding suspended often one, two, or three kinds of 
anatomical elements, the humors are more. complicated 
than those elements, while they are less so than the tissues. 
For a long time the exclusive property of chemists, the 
study of the humors, thanks to Robin, has once more taken 
its natural and proper place in the series of anatomical 
studies. These moving organs are studied with the same 
system, by the same processes, and in the same spirit of 
subordination to physiological and pathological experiences, 
as the firm and immovable organs placed in a fixed position. 
Robin has thus done for the humors what he had al- 
ready done for immediate principles and anatomical ele- 
ments. He has put them in their true place, has classified 
them and pointed out their function in the generality of 
organic acts. He divides animal liquids into three classes: 
the constituent humors, the secretions, and the excretions. 
And there is a positive satisfaction for the mind in the 
picture he gives us of the relations of these three classes 
