COAGULATION OF BLOOD OF ARTHROPODS. 303 



having apparently most carefully removed the shreds, one fre- 

 quently sees under the microscope a small mass of blood cor- 

 puscles which had not been removed from the blood, in the 

 center of a small gelatinous coagulum. 



In many cases, however, a second coagulation after having 

 removed most of the shreds does not take place even if some of 

 these shreds have remained. In the cases in which it does take 

 place it is also possible that the cell protoplasm, derived from the 

 solution of so many blood cells, may be sufficient to cause 

 coagulation even if the absolutely intact blood cells themselves 

 have been entirely removed. It may be found that by adding 

 water to the blood during the first coagulation and afterwards 

 filtering the diluted blood, the second coagulation can be inhib- 

 ited with quite a certainty for a longer period than otherwise, or 

 may be even entirely prevented. Dilutions of the blood there- 

 fore produce an absolute diminution in the formation of fibrin for 

 a certain period, not only a relative one in proportion to the 

 remaining fluid. 



In the experiments made such diluted serum was afterwards 

 distributed in small dishes, 4 or 5 cc. into each dish ; different sub- 

 stances were added to several of those dishes to determine the 

 influence of these substances on coagulation. 



It could be shown that the addition of about two or three 

 pieces of shreds of fibrin derived from the first coagulation of the 

 lobster blood had a very pronounced effect on the coagulation of 

 the diluted serum. Without the addition of such fibrin coagula- 

 tion either did not take place at all, or only after some hours or 

 on the next day. The difference in the dishes with shreds of 

 fibrin and those without the fibrin was very marked. The 

 influence of these shreds derived from the first coagulation was a 

 localized one, the clotting always beginning directly around the 

 pieces of fibrin and from here advancing concentrically towards 

 the periphery of the fluid. 



The fibrin however produced by the first coagulation is not the 

 only substance having such an effect ; pieces of muscle of the 

 lobster act about equally well. In these experiments the muscle 

 was carefully washed so that all blood was removed. The fibrin 

 of the blood of rabbits or rats, or muscle of frogs, was without 



