35 



Ihoi'Dugli iiiicroscojjical exaiiiinalion on nccoiml of ils per- 

 fect transparency. 



Frequently it has l)een endeavoured to modify the cul- 

 ture medium to ma]<e it simpler, i. e.. to get a supj)orling 

 material of a more indifferent character and of better 

 known composition than the fibrin meshwork. Agar, gela- 

 tin, glass wool, silk gauze, spider w-ebs, cotton tlii'eads, etc., 

 have been tried, and all can be used as a framework for 

 the outgrowing cells, but none of them is able to give sup- 

 port for as uniform an outgrowth as does the fibrin. When it 

 so often is referred to that Lewis and Lewis use so 

 simple a culture mediiun as Ringer's solution or even sea- 

 w^ater, it is somewhat confusing. The outgrowth finds its 

 support on the coverslip itself and the tissue grows for a 

 short time at the expense of the growth-i)romoting sub- 

 stances in the tissue fragment itself. These experiments ai'e 

 often referred to, to show how simple it is to cultivate tis- 

 sue. For the inexperienced it may therefore be understood as 

 though the cells can be cultivated in a liquid and without 

 any nourishing sul)slances. The use of the surface of the 

 coverslip as a sup])orting apparatus is very good so far, but 

 it is not a safe method to get outgrowth for any length of 

 time. To get a growth on the cover slip or any other two- 

 dimensioned support, it depends very largely on the con- 

 tact of the tissue with the su]3por[; mostly those cells 

 which arc in direct contact with the glass will migrate. It 

 is different when the tissue is imbedded in the plasma 

 clot and perfectlj^ surrounded by a fine meshwork; then 

 there will always be a sufficient and good contact between 

 the cells and the supporting apparatus. The fibrin clot can 

 be considered as a fine sponge of fibrin threads nolding 

 the liquid in its meshwork. In between these two phases of 

 liquid an(i solid, the tissue cells migrate. 



This fibrin system seems to be unsurpassed as a culture 

 medium for the cells. The fibrin-threads do not show up 

 in the microscope and it is therefore an excellent transpa- 



3* 



