Tue Microscope. 183 
independently of the plaques, particularly if healthy blood be 
examined in which plaques are not very numerous. When 
there is an abundant formation of fibrin the network of threads 
is seen all over the field, and every spot is full of fibrin; but 
when the fibrin is not abundant it will almost always be seen 
that the fibrin is thickest in the vicinity of the masses of plaques. 
“ Even in preparations where the fibrin is sparingly formed, the 
threads are deposited elsewhere than around the granular 
masses, and occasionally, though rarely, I have found granular 
masses around which the fibrin did not appear to lie more thickly 
than in the clear field. The fact that nearly always the fibrin 
is deposited most thickly around the granular masses, even ra- 
diating from them as centres, while interesting and significant, 
is not conclusive proof that the plaques are connected with co- 
agulation ; for the same adhesive property of the plaques which 
makes them adhere to each other, may also cause the threads to 
stick fast as they separate out from the medium around them. 
This seems all the more probable when we consider that the 
fibrin as well as the plaques is sticky and adheres to the glass”’ 
(Kemp). The fact that in preparations in which the clot is 
scanty the fibrin is deposited more thickly in the vicinity of the 
masses of plaques may possibly be due to the plaques giving up 
something which causes or hastens coagulation, and that in di- 
lute solutions this substance is more abundant in the vicinity of 
the granular masses than elsewhere. 
Laker has taken the ground that the fibrin-threads are folds 
of a membrane which he calls the primary fibrin membrane; a 
view almost identical with that taken by Virchow in 1856. 
Kemp concludes that what Laker describes as a membrane is 
a layer of the homogenous substance described by Virchow, 
Rindfleisch and Hermann, which is essentially of the same com- 
position as fibrin, and from which the fibrin-threads are formed 
by a process very closely resembling crystallization, if not iden- 
tical with it. Hermann thinks that the threads are formed bya 
process which closely resembles crystallization, and Schimmel- 
busch insists most positively that the formation of fibrin-threads 
is a true crystallization process, nor does he believe that there 
is a previous stage, either homogeneous or granular. Hayem, 
though not believing in the fibrinous character of the plaques, 
