374 The Microscope. 



to think that some element is present in mammalian blood which 

 also acts as a factor in coagulation. The coagulation of the frog's 

 blood begins with the grouping of the " haematoblasts " into a rosette 

 form. The red corpuscles then arrange themselves radially about 

 this point as a centre. Do we find an analogous process at the com- 

 mencement of the coagulation of mammalian blood? The blood of 

 mammals coagulates very rapidly, whereas that of the frog changes 

 very slowly; hence, if we would study the blood of mammals before 

 coagulation, we must prevent this process by means of some reagent. 

 Such an experiment cannot be tried with a human being, but is 

 easily made with a dog. The reagent usually employed is peptone, 

 which is injected in solution into the jugular vein of the dog, the 

 amount injected being 0.8 grain peptone for every kilogramme weight 

 of the dog. The. microscopical examination of blood in which 

 coagulation has thus been prevented, shows that there exist in the 

 blood, aside from the other elements, tiny tablet-like granules which 

 tend to cling together in clumps. These elements were described 

 by Bizozerro, and called by him " Blutpliittchen." It thus seems 

 probable that the " Blutpliittchen " have something to do with the 

 coagulation of the blood. That they also exist in human blood is 

 evident from their presence in our preparation as small, faintly- 

 tinged bodies, which lie in groups of twos and threes together. 

 They did not disappear from the blood Ave employed, because we did 

 not give it time to coagulate before fixing it. Therein lies the 

 advantage of . this method in the examination of human blood. It 

 gives lis not only the possibility to distinguish the different elements 

 of the blood, but through it, it has been possible to discover elements 

 which, like the " hfematoblasts," accompany the phenomenon of 

 coagulation, and also to determine in part the relation that exists 

 between the elements. It would not agree with the general plan of 

 nature if every form did not play a different role in the organism, 

 and after all that has been discovered it is not improbable that we 

 shall one day be able, through watching the changes which the dif- 

 ferent elements undergo in the blood, to discover the disturbances 

 caiised by different ferments and organisms in the blood. Thus we 

 think that the hope of clever physicians may one day be verified, 

 that the analysis of a drop of blood may give a clue to the patholo- 

 gical changes in the body. — Am. Naturalist. 



Preparing Eggs of Rotatoria. — In the Zeitschrift f. Wis. 

 Zoologie, Dr. Tessin gives an account of his diificulty in obtaining 

 good preparations of the small eggs of Rotatoria. His process with 



