112 ORGANISED FLUIDS. 



Unlike, however, in one respect the blood itself, which in a 

 state of health is alkaline, the menstrual fluid is acid, its 

 acidity arising from its admixture with the vaginal secretion. 



Transfusion of the Blood. 



It has been stated, and the statement is most probably 

 correct, that between the size of the blood corpuscles and 

 that of the capillaries of the same animal, an exact relation 

 exists, and it is by reference to this fact that the fatal effects 

 which have so often ensued, from the transfusion of the 

 blood of one animal into the vessels of another have been 

 apparently so satisfactorily explained. The little vessels, it 

 has been said, are too small to admit the larger globules of 

 the new blood ; a mechanical impediment is thus offered to 

 the circulation of the blood in the capillaries, which stagnates 

 in them, giving rise to constitutional disturbance, and ultimately 

 to death. This explanation, plausible as it appears, has been 

 shown by recent experiments to be erroneous, and that the 

 true cause of the fatality which has so often attended the 

 operation of transfusion, depends upon the difference which 

 exists in the qualities of the fibrin in the blood of two different 

 animals, or even of two distinct individuals : this is shown by 

 the fact that the transfusion of blood deprived of its fibrin 

 is never followed by the serious results to which reference 

 has been made. Notwithstanding this fact, it is yet very 

 evident that if the blood of an animal, the corpuscles of 

 which are much larger than the human blood disc, and at the 

 same time are of a different form and structure, such as for 

 instance those of some birds, be introduced into the vessels 

 of man, a very serious and probably fatal mechanical im- 

 pediment would be presented to their circulation through the 

 capillaries. Blood corpuscles of a circular form, and but 

 little larger than those of man, might indeed make their way 

 through the vessels in consequence of the plastic nature of 

 the globuKne which composes them. 



The new globules thrown into this system by the operation 

 of transfusion, although they would circulate for a time with 



