COAGULATION OF BLOOD OF ARTHROPODS. 305 



The addition of I cc. of water and 6-4 per cent, sodium chlor- 

 ide solution to the serum had in most cases but a slightly inhibit- 

 ing effect. 



In such solutions coagulation has occurred occasionally even 

 more rapidly than with the pure serum ; an accidental admixture 

 of a larger number of blood cells to this liquid may perhaps have 

 been the cause. All these experiments, as well as most of the 

 following ones, were made with the addition of shreds of fibrin 



o 



obtained from the first coagulation of the lobster blood. 



The addition of I cc. of a I per cent, solution of potassium 

 cyanide or of a 1 6 per cent, solution of Witte's peptone, or of a 

 saturated solution of urea, had a decidedly inhibiting effect. The 

 peptone solution prevented the coagulation entirely ; the potas- 

 sium cyanide and urea solutions frequently had only an inhibiting 

 action for some time, after perhaps 16 hours (sometimes earlier) 

 coagulation usually occurring. Generally only half an hour 

 after the addition of these substances their effect became notice- 

 able. The order in which these substances, according to their 

 strength, acted on the serum, was the following : Potassium 

 cyanide had the weakest and Witte's peptone the strongest action ; 

 urea stood between these substances. 



If, however, the experiments were made in this way, that the 

 pieces of the first fibrin were in the beginning put for some time 

 into potassium cyanide, urea or peptone solutions, then after hav- 

 ing been washed out, put into dishes containing the blood serum, 

 the order of the loss of efficiency of the fibrin was reversed. 

 Pieces having been kept for one half hour to two hours in 

 peptone solution, were almost as effective as fresh fibrin, even 

 pieces having been kept in peptone over night were frequently 

 still very active, although in many cases they had lost a consider- 

 able part of their efficiency. It is of importance that the peptone 

 be well washed out for some hours, otherwise the peptone, be- 

 coming extracted and dissolved in the serum, prevents its coagu- 

 lation. 



Pieces having been kept for one half to two hours in a solution 

 of urea and having been afterwards well washed, have lost the 

 greatest part of their efficiency, and after having been kept for 

 twelve hours have become absolutely ineffective. 



