COAGULATION OF BLOOD OF ARTHROPODS. 315 



which the blood corpuscles have spread out, the appearance of 

 connective tissue is presented. We see apparently infect cells sur- 

 rounded by fibrils. These cells, however, only represent the 

 endoplasmodic part of the original blood corpuscles, the exoplas- 

 matic part having been transformed into fibrils. Many of these 

 fibrils stain very well by Mallory's connective tissue stain. 



In a similar way, the fibers of fibrous tissue and of neuroglia in 

 mammalians seem to be produced from the exoplasm of the cells. 

 In coagulating blood, however, whole cells may be changed into 

 fibers. Here protoplasm having left the cell body and being now 

 entirely intercellular may also form fibrils. Such an occurrence 

 can easily be observed under the microscope in the blood, these 

 changes taking place in a short time. It would be more difficult 

 to prove such an occurrence in the development of connective 

 tissue. The morphological similarity (not identity) between the 

 processes in the blood cells and connective-tissue cells being 

 apparently so great, it ought to be considered, whether an inter- 

 cellular origin of fibers from protoplasm, secondarily discon- 

 nected from cells may not also take place in connective tissue. 



We can observe that the granules of the blood cells frequently 

 spread out and assume in the end an intercellular situation, and that 

 they not infrequently become included in fibrils. Similar obser- 

 vations have been made in the developing cartilage for instance. 



As we have seen, the formation of intercellular substances in 

 the coagulating blood can be prevented if we collect the blood 

 cells in certain solutions, which inhibit that further changes in 

 the cells take place without preventing the possibility of such 

 changes, if the solution is changed afterwards. We may there- 

 fore say that one of the conditions under which the formation of 

 an intercellular substance takes place is the presence of a certain 

 fluid which surrounds the blood cells which have left the body. 

 The serum has therefore a more or less cytolytic power and the 

 formation of "connective tissue" is based on a partial destruc- 

 tion or dissolution (cytolysis) of the blood cells by which proto- 

 plasm leaving the cells becomes changed into intercellular fibrils. 



SUMMARY. 



i. The following factors play a part in the coagulation of the 

 blood of arthropods : 



