TRANSFUSION OF BLOOD 139 



discoveries lead to results which are apparently irreconcilable, 

 and contrary to the general ideas which inspired their 

 departure; yet in the end all these routes lead to a clearing 

 from which one can survey easily all the roads, and where 

 everything can be explained and mutually understood. 



During the study of immunity such phenomena have been 

 discovered that it seemed impossible to find common bonds, 

 or to reconcile them with the laws which logically followed 

 the discoveries of Pasteur; we shall see that it has become 

 possible today to assemble all these phenomena into one 

 harmonious whole which, far from contradicting, confirms 

 Pasteur's ideas and completes them by new laws. 



TRANSFUSION OF BLOOD AND INJECTION OF HETER- 



OLOGOUS AND HOMOLOGOUS SERA AND 



OTHER PROTEINS. 



For a long time (since the old Egyptians) it was known 

 that it was possible to "transfuse" blood from one animal 

 to another, and that transfusion between animals of the 

 same kind was less dangerous than transfusion between 

 animals of different kinds; but it was to Landois, and espe- 

 cially to Hayem 1 (1885-1890) that we owe the first precise 

 experimental studies of this question. Among other experi- 

 ments Hayem injected blood from cattle into the veins of 

 dogs, and determined that while a first injection of about 

 50 c.c. is endured without noticeable reaction, a second 

 injection, of a dose half as strong, into the same animal twelve 

 days after the first injection, is followed several minutes 

 later by a violent crisis generally ending in death. 



"The blood of an animal so treated," writes Hayem, "con- 

 tains elements more or less changed, and sometimes hyaline 

 concretions which are very refracting and extremely viscous. 

 The blood in a tied vessel, kept from the previous day, 

 remained liquid; there was a formation of clots like a sedi- 

 ment. It is these small masses of albuminoid matter (forma- 

 tion of a precipitate) which are the origin of the emboli. 



1 On Blood and its Anatomical Alterations, Paris, 1889, pp. 240 et seq. 



