')') 



II is remarkable how coniplclcly the lorhniqiic was 

 worked out rroni llie very l)eginnin<f. Tliis ean be seen by 

 all the expeiimenis which have lalei- been allenipled, for 

 instance, lo eiKh'avoui' lo inodilN the ciillure niediuni. io 

 obtain another sn])portin<f a|)paraliis loi* the tissue cells 

 to grow on. All that has been tested as a substitute for one 

 or another of the constituents ot the plasma-tissue juice 

 medium, has been so far without success. It seems that the 

 only satisfactory method was accomplished from the very 

 outset. 



In ])ractically all branches of exi)erinienlal medicine a)id 

 biology the method of cultivating tissue has been applied 

 already. As a morphological and physiological method, the 

 tissue cultivation method of explantation was introduced 

 when R. G. Harrison 249) solved the fundamental ipies- 

 tion of nerve regeneration as an active cell movement and 

 growth of the axis cylinders by studying the phenomenon 

 in vitro. After these successful experiments several morpho- 

 logists took up the method for the study of other jiroblems. 

 Studies of cell divisions, cell degenerations, were under- 

 taken. The histogeny of the various cell products, as for 

 example connective tissue fibrils, was studied. This can be 

 referred to in the works of L e wm s and L e w i s, M a x i- 

 m o f f, L. Loch, B a i t s e 1 1, L a m b e r t and H a n e s, 

 Uhlenhulh. ()pj)el. C-hampy and several others. 



It seems to be the morphology which has interested most 

 investigators; probably because of the less difficult techni- 

 que for making morphological studies. An explanted frag- 

 ment of tissue of any kind is a rather easy matter to keep 

 living in vitro for a short period (from a few hours to 

 several days) and one can still observe an outgrowth or 

 migration of cells, besides some active cell divisions. For 

 those experiments of short duration, the composition of 

 the culture medium does not play any important role. 

 As Lewis and Lewis 327) 349) 350) have shown, an 

 outgrowth of cells can be observed in a simj)le fluid con- 



