64 



MANUAL OF HISTOLOGY. 



of acetic acid are to be added so that the solution shall not con- 

 tain more than 1 per cent, of acid, and then mount in glyce- 

 rine. It will then be seen that the softest portion contains 

 numbers of irregularly-shaped, thin plates, some provided with 

 an oval, flattened nucleus, others having none that are appa- 

 rent (Fig. 23). Some of these flattened bodies anastomose by 

 these processes with those of other plates, others are quite free. 

 The substance tying between the cells, the intercellular sub- 

 stance, is quite homogeneous, or slightly granular, in the softest 

 portions, and has at first no defined fibrillation. In the neigh- 

 borhood of the former tissue, lines of fibrillation occur, while at 

 the same time these flattened bodies become smaller, although 

 they are still flattened (Fig. 24, b). Mucous or gelatinous tissue, 



FIG. 24. Connective tissue in an advancing stage of development. From the umbilical cord. 



as it is seen in the umbilical cord of an embryo, is properly an 

 embryonic or developmental form of connective tissue which is 

 never found in normal adult life. All the phases of develop- 

 ment may here be seen, from the most primitive, comprised in 

 Wharton' s jelly, to the firm, fibrous fascicles that encircle the 

 vessels. 



Properly speaking, the true mucous tissue is, as its name 

 implies, a viscid material, and, indeed, is much like half-set 

 glue, in which the corpuscles are scattered with little or even 

 no cohesion. 



The intercellular substance differs from albumen in not con- 

 taining sulphur ; from chondrin and gelatin, in not being pre- 

 cipitated by boiling, tannin, or the bichloride of mercury. 



