Franklin P. Mall 333 



cell body itself is irregular in shape, running out into small elevations, 

 or points, from which fine threads of protoplasm without pigment 

 radiate. Occasionally one of these radiations reaches to and blends 

 with a protoplasmic process from a neighboring cell. There is every 

 indication of the beginning of an extensive syncytium formed by cells 

 of the mesenchyme. 



That the cells of the mesenchyme unite is a well known fact and can 

 easily be demonstrated in frozen sections, and in teased specimens of the 

 umbilical cord. In addition I need only to refer to the description and 

 illustrations of Flemming "^ and of Spuler. " Die mit einander vielfach 

 in netzartigem Zuzammenhang stehenden Zellen des jSTabelstranges sind 

 ueberwiegend spindelformig odor 3-4 zipfelig und sind an den Enden in 

 feinsten Fibrillen aufgefasert, bald dicht an der Zelle, bald erst nachdem 

 ein Fortsatz sich ueber eine langere Strecke bin kompact erstreckt 

 hat." ' 



The syncytium as seen in tadpoles 3 .mm. long progresses rapidly to 

 form a definite tissue from which only connective tissues arise. The 

 mesenchyme has already divided into at least two groups of tissues in 

 the embr3'o, one destined, to form muscle and the other connective 

 'tissue. The syncytium destined to form the connective tissue, which I 

 shall term the connective-tissue syncytium, begins to have its charac- 

 teristic form at this time, and in its further growth it either remains as 

 it is or gives rise to the connective tissues as we ordinarily understand 

 them. 



The point I wish to leave open is whether or not the mesenchyme was 

 ever composed of individual cells. Was it not a syncytium throughout 

 its development ? The most valuable and suggestive studies of His ° 

 will have to answer this question for the present. At any rate, it is 

 quite evident that the earlier syncytium, if it exists, is a very incomplete 

 one, with very loose protoplasma bridges, easily broken and easity united 

 to allow the cells to wander in all directions during the earliest stages 

 of development. So it may be that the syncytium as seen in the tadpole 

 3 mm. long has existed ever since the appearance of the mesenchyme. 



In a tadpole 4 mm. long the amount of mesenchyme, or connective- 

 tissue syncytium, has increased a great deal around the brain, myo- 

 tomes, etc. Around the anterior end of the chorda it is again very 

 definite and can be studied better than elsewhere on account of its 



6 Flemming, His' Archiv, 1897, S. 183. 

 ■f Spuler, Anat. Hefte, viii, 133. 



8His, Zellen uud Syncytialbildung; Protoplasmastudien ; Lecitboblast und Angio- 

 blast. Abhandl. d. K. S. Gesellschaft d. Wiss., Bd. 34, 2.5 u. 26, 1898-1900. 



