No. 3-] BLOOD-PLATES OF THE HUMAN BLOOD. 65 1 



tended investigations, but can only point out a few observations 

 which I believe have not been recorded by others. In my 

 former paper on the plasmocytes, attention has been called to 

 the fact that these plasmocytes actually engulf and digest food, 

 such as bacteria and debris of erythrocytes and other cells, and 

 that they frequently possess in their interior one or more 

 highly refractive granules, which it is suggested may be food 

 granules, stored for future use. The plasmocytes of the human 

 blood are too minute to allow of a detailed investigation of any 

 such engulfed food particles, but still they are sufficiently large 

 to enable us to clearly distinguish the presence of highly refract- 

 ive granules of the same nature as those in the plasmocytes 

 of Batrachoseps, and similarly located as regards the various 

 spheres.' 



In coagulated blood and in thrombosis the finer structure of 

 the blood-plates appears to be greatly confused, and so far I have 

 not been able to devise any method by which this structure can 

 be satisfactorily studied under these conditions. I have found 

 in coagulated blood many highly refractive granules scattered in 

 the serum, but am not certain that they can be considered iden- 

 tical with the highly refractive granules of the blood-plates and 

 plasmocytes. The similarity is sufficiently great, however, to 

 suggest that possibly these granules are not really food granules 

 stored for future use, but that they are secreted granules, per- 

 haps a ferment causing the coagulation of the blood when ejected 

 from their place in the plasmocytes into the blood serum. 



The highly organized structure of the blood-plates indicates 

 that they cannot, as has been supposed by many, be originated 

 in the blood with great rapidity and precipitated at the very 

 moment that they are required. The blood-plates must pos- 

 sess a phylogenetic life cycle, through which they have acquired 

 structure, increased by growth, accumulated food, and secreted 

 certain highly refractive matter. In a word, the blood-plates 

 must be considered an independent element of the blood, of 

 equal rank with the red and white corpuscles, and of hardly 

 less importance. 



' Since the above was written I have repeatedly found in the human blood 

 blood-plates which contained debris of erythrocytes. 



