4 Blood-Relatioiisliips 



a common property has persisted in the bloods of certain groups of 

 animals " throughout the ages which have elapsed during their evolu- 

 tion from a common ancestor, and this in spite of differences of food 

 and habits of life." The persistence of the chemical blood-relationship 

 between the various groups of animals serves to carry us back into 

 geological times, and I believe we have but begun the work along 

 these lines, and that it will lead to valuable results in the study of 

 various problems of evolution. 



In the following pages I have given but a brief and fragmentary 

 summary of the immense amount of work which has been done on 

 antibodies other than the precipitins, my object in mentioning them 

 at all is to bring out the many points of resemblance between the 

 different antibodies. On the other hand, I believe that this con- 

 stitutes the first attempt to treat the subject from a general and 

 more especially zoological point of view. The literature relating to 

 the precipitins has been gone into as fully as possible. In view of 

 its scattered nature, a summary and criticism of our knowledge brought 

 up to date should prove of value, more especially to English readers. 



Comparative studies upon the constitution of the bloods of different 

 animals by means of ordinary chemical methods have not demonstrated 

 differences such as can be proved to exist by means of what we may 

 well call the biological methods, the use namely of the precipitins and 

 haemolysins. It is true that Abderhalden and others have demonstrated 

 that chemical differences of a coarser nature exist between the bloods 

 of Carnivora and Herbivora, that a similarity exists between the blood 

 of the sheep and ox, etc., but the investigations afford no means of 

 demonstrating delicate differences such as we have been able to study 

 by means of biological tests. 



In view of the crudity of our methods, it is not surprising if certain 

 discrepancies may be encountered in the course of investigations con- 

 ducted by biological methods, the body of evidence is however perfectly 

 conclusive. The object of my investigation has been to determine 

 certain broad facts with regard to blood-affinities, consequently my 

 studies must be regarded in the light of a preliminary investigation, 

 which will have to be continued along special lines by many workers 

 in the future. 



