580 ANNUAL EEPORT SMITHSONIAN INSTITUTION, 1910. 



fying tubules were produced. In the cultures of kidney, tubules, 

 the wuU of which is covered with epithelium cells, may grow out 

 from the original fragment. We observed also chains of large 

 epithelial cells radiating out from the fragments of liver. From 

 the edges of fragments of skin gi*ow out layers of epithelial cells, 

 which cover sometimes a surface larger than the surface of the 

 original fragment. 



Epithelial and connective tissues cultivated in vitro increase really 

 in size, and the new tissue is formed by the wandering of the cells 

 from the original fragment and by their multiplication. Camera 

 lucida drawing of a rapidly growing sarcoma showed that the origi- 

 nal fragment of sarcoma and of spleen grows very actively, the 

 original tissue resolves itself in living cells after a few days and dis- 

 appears almost completely. At the same time there is multiplication 

 of the cells. In the cultures fixed and stained with hematoxylin, 

 karyokinetic figures may be seen on all the surface covered by the 

 new cells. In slowly developing cultures of peritoneum we have seen 

 karyokinetic figures 14 days after the preparation of the culture. 

 We have observed also in living cultures direct division of the nuclei 

 and the production of giant cells. The multiplication of the cells 

 can easily be followed under the microscope. Wlien a fragment of 

 plasma containing a few cells is extirpated from a culture of spleen 

 or of thyroid gland and transplanted into a new medium the cells 

 can easily be observed. During the hours and the days following 

 the preparation of the new culture, the cells are seen increasing in 

 number, wandering out from the plasma and invading the new 

 medium. After a few days a very large number of cells have grown 

 from the few transplanted cells. 



It seems, therefore, that in our experiments there is a real culti- 

 vation of tissues, since the fragments of tissues grow progressively 

 into the culture medium, that the fragments of kidnej^, thyroid gland, 

 liver, and skin produces tubules, chains, or continuous layers of 

 epithelial cells, since the fixed cells of the tissues, instead of becom- 

 ing necrotic, may wander into the medium after more than 10 or 12 

 days, since this medium contains many karyokinetic figures and since 

 a few isolated cells can be seen producing a very large number of 

 new cells. 



During the development of cells the culture medium undergoes 

 marked modifications. Sometimes the plasma does not coagidate, or, 

 as it happens in the cultures of human carcinoma and of certain 

 glandular tissues, it coagulates and after a few hours it liquefies 

 again. In these cases no growth is observed. Generally the clot 

 remains firmly adherent to the cover glass and to the tissue. If 

 a part of the fragment is dead a retraction of the plasma may occur 

 in this point after a few days. When the tissue grows normally, 



