PREFACE. 



r I iHE investigations recorded in this volume were carried out in the 

 -*~ Pathological Laboratory of the University of Cambridge, chiefly 

 during the year 1902. 



My original intention was to publish a volume on the demonstration 

 of certain blood-relationships amongst animals as indicated by 16,000 

 tests made by myself with precipitating antisera upon 900 specimens 

 of blood obtained from various sources, followed by a critical review 

 of the literature on antibodies in blood. 



Subsequently it was deemed advisable to add a section dealing with 

 the practical applications of the precipitin test for blood in legal 

 medicine, together with some investigations carried out at my sug- 

 gestion by Messrs G. S. Graham-Smith and F. Sanger. The latter were 

 published in the Journal of Hygiene, vol. III., 1903, but are added for 

 the reason that they bear directly on the subjects treated in this volume. 

 Finally two new sections were added dealing with further original 

 researches conducted in this Laboratory. The latter are entitled " The 

 Results of 500 Quantitative Precipitin-Tests upon the Bloods of Primates, 

 Insectivora, Carnivora, Ungulata, Cetacea, Marsupialia and Aves " by 

 myself and Mr T. S. P. Strangeways, and " Blood-Relationship amongst 

 the Lower Vertebrata and Arthropoda, etc." by Mr G. S. Graham-Smith. 



The results recorded in these papers should be of interest not only 

 to zoologists, physiologists, and those engaged in practical medico-legal 

 work, but also to those interested in the complex problems of immunity. 



Although the source from which each specimen of blood was obtained 

 has been fully acknowledged in the text, I here wish to place on record 



