Franklin P. Mall 33D 



ent slimy mass, dii'Ecult to handle or to stain in any very satisfactory 

 way. In pepsin the section becomes firmer, opaque, brittle, and it must 

 be crushed to separate the nuclei in order to study the syncytium, in 

 case it is not digested. Quite satisfactory results are obtained by 

 digesting sections of embryos, which have been attached to glass slides 

 by the water method. It is of course necessary to use sections from 

 embryos which have been hardened in alcohol, in order to obtain results 

 similar to those obtained from frozen sections, Not only does this 

 statement apply to embryos but to tissues in general. With pancreatin, 

 however, the digestion upon the glass slide is very unsatisfactory, for 

 the alkali in the solution nearly always detaches the sections, probably 

 on account of the great amount of mucin in them. The younger 

 the embryo the more difficult it is to retain the sections upon the glass 

 slides. 



Not only is it difficult to obtain fairly good sections which have been 

 digested, but there is in addition the complication of unequal as well as 

 contradictory results. When one point appeared to be worked out in 

 a satisfactory manner, later tests contradicted it, and so on. It is 

 therefore with some hesitancy that I give the tests with digestive fer- 

 ments upon the connective-tissue syncytium. 



In general it is quite certain that when the main mass of the syncy- 

 tium is formed of exoplasm it is digestible in pancreatin and bicar- 

 bonate of soda. This treatment causes the section, if fresh, to become 

 a swollen and slimy mass in which the delicate fibrils can be seen after 

 it is treated with picric acid. The ground substance of the cartilage, 

 if present, is well isolated and the more developed fibrils of the peri- 

 chondrium can also be seen. It appears that the more the syncytium 

 is differentiated the more it resists pancreatic digestion. In case a 

 section of an older embryo is digested upon the glass slide it will be 

 found that at the end of 3-4 hours all of the nuclei are dissolved, while 

 all of the fibrils of the exoplasm of the S5^ncytium, the white fibrils and 

 the ground substance of the cartilage remain. In a section of this kind, 

 which includes the umbilical cord, all stages of the syncytium can be 

 studied; that in the cord is not differentiated, while that toward the 

 back is changed into white fibrous tissue and cartilage. In the aorta 

 there are at this time numerous elastic fibers. With Mallory's stain it 

 is shown that a beautifuL network of fibers alone remains, the nuclei 

 having begn digested in the pancreatin. Furthermore, it is shown by 

 staining with Weigert's elastic tissue stain that the elastic fibrils have 

 also been dissolved. The above-named tests were made many times on 

 embryos from 7 mm. to 20 cm. in length. The older the tissue the 



