354 Tlie Development of the Connective Tissues , 



reticulum as a separate tissue and will not enter upon the discussion " 

 of this subject at present. At any rate, if these reasons are overcome, 

 reticulum will remain as peculiar white fibrous tissue not fully devel- 

 oped, in case we can consider any tissue in the adult body as embryonic. 



In examining various tissues for the development of reticulum, I 

 found that in the liver it arises from Kupffer's endothelial cells, which 

 here also form a beautiful syncytium.'" 



Frozen sections of the liver of a pig 3 cm. long are very delicate, and 

 can easily be crushed under a coverglass. When such preparations are 

 stained with a little magenta it is seen that a network of fibrils lies 

 between clumps of liver cells. It can now be determined that all of the 

 fibrils surround the capillaries and are formed by prolongations from 

 Kupffer's cells. The fibrils, or rather the syncytium, is delicate, can 

 easily be stretched and broken by slight pressure upon the cover glass. 

 Such sections are also very easily broken into granules by giving them 

 a delicate shake in water. When digested a short time in pancreatin at 

 room temperature the liver cells break up and fall out, leaving the 

 delicate syncytium to which are attached many small granules. In 

 such preparations the syncyidum is still very elastic and does not appear 

 to swell in acetic acid. 



The observations upon the development of the reticulum of the 

 liver are entirely out of harmony with those of the development of 

 connective tissue elsewhere. In all other places the syncytium arises 

 from the mesenchyme but here it is from the endothelial lining of 

 blood-vessels. 



It is not difficult to obtain fresh specimens with all the capillaries 

 surrounded with this syncytium which has the nuclei imbedded in it; 

 the union is so complete that it is impossible to consider the nuclei and 

 exoplasm in apposition only. The fibrils are in no way connected with 

 the liver cells and true mesenchyme cells are not present at all. 



The Coenea. 



.The cornea of a pig 2 cm. long is composed of a dense syncytium. 

 The exoplasm is fibrillated and it radiates from nodal points where 

 are located the nuclei and endoplasm. In an embryo 3 cm. long 

 the general direction of the fibrils of the exoplasm is parallel with 

 the surface of the cornea, i. e., the lamellse are beginning to form. 

 Between these primitive lamellfe the nuclei lie and are surrounded by 



11 Mall, Zeit. f. Morpholog. u. Anthropol., ii, 9. 

 '■^Kiipffer, Archiv f. mik. Anat., 54. 



