466 Messrs. W. Cramer, A. H. Drew, and J. C. Mottram. 



capillary systems of the viscera. Those bacteria which are not agglutinated 

 remain in the circulation and produce a progressive septicaemia. Generally 

 speaking, comparing different types of bacteria, the degree of the agglutination 

 of the infecting bacteria in the circulation of the host is a measure of the 

 resistance of the host to the particular types of organism. Bull drew special 

 attention to the fact that with typhoid bacilli, for instance, the mechanism of 

 defence in the living body is very different from that observed in vitro by 

 serum or defibrinated blood. In the latter destruction is caused by bacterio- 

 lysis, while in the living animal there is the process of agglutination and 

 subsequent phagocytosis in the organs described above. Delrez and 

 Govaerts (7, 8) have followed up these observations, and have shown that this 

 process of agglutination in the living animal is brought about by the platelets. 

 They found that a few minutes after the injection of certain bacteria there is 

 an agglomeration of the platelets and the bacteria. A few minutes later the 

 masses of agglomerated bacteria and platelets can be found in the liver under- 

 going phagocytosis. 



The thrombopenia, which is produced in guinea-pigs by the injection of an 

 antiplatelet serum (the experimental purpura of Ledingham (9) ), does not 

 lead to the development of infective conditions, because the animals either 

 die within a few days as the result of the haemorrhages, or when they recover 

 the thrombopenia rapidly passes off. The thrombopenia alone is, as Bedson (10) 

 has shown, not sufficient to produce haemorrhages. These are the combined 

 result of the thrombopenia and of a lesion of the vascular endothelium 

 produced by the antiplatelet serum. 



Summary. 



The absence of the fat soluble vitamin from the diet always leads in the 

 rat to a progressive diminution in the number of blood platelets. This 

 thrombopenia is the only constant lesion which we have found, so far, in every 

 case of vitamin A deficiency, and we regard it as the lesion characteristic of 

 this deficiency, just as the lymphopenia is characteristic of the vitamin B 

 deficiency. A thrombopenia may even be found in rats kept on a vitamin A 

 free diet when they do not yet show any obvious signs of ill-health, and are, 

 to all external appearances, normal animals. When a profound thrombopenia 

 has been established, the addition of the missing vitamin A to the diet is 

 followed by a rapid increase in the number of platelets to the normal number, 

 provided that the animal has not been allowed to suffer too long and too 

 severely from the deficiency. 



Exposure to radium produces not only a lymphopenia, but also with 

 sufficiently large doses a thrombopenia, From this the animals recover 



