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MANUAL OF HISTOLOGY. 



tive-tissue fibrillse. Elastic fibres make their appearance also by the trans- 

 formation of the same substance (see below, with connective-tissue). The 

 cells again frequently take on a more elongated, narrowed form. If the 

 whole series of transformations passes over them to its conclusion, which 

 is by no means always the case, what is known as formless connective- 

 tissue is formed. 



After this general description, let us subject the enamel organ and 

 umbilical cord to nearer examination. The first of these covers the germ 

 of the rudimentary tooth during intra-uterine life and the earliest years 

 of infancy. 



Its tissue (fig. 181) consists of delicate stellate cells with distinct nuclei. 

 The latter are vesicular in the embryo of four months, measuring 0-0066- 

 0-0090 mm., whilst the cell with its processes shows an extent of 0-0260- 

 0-0385 mm. The number of these latter is at times only four (a), but 

 often far greater (a, b). There occur also cells with double nuclei, and at 

 times a species of segmentation is observed (6, below). 



The interstices between the cells so united to one another attain a 



breadth amounting to 

 0-0204-0-0320 mm. and 

 upwards, and are filled 

 with a homogeneous gela- 

 tinous mass, which gives 

 to the whole enamel organ 

 the same consistence vary- 

 ing in density according 

 to its amount. 



That we have here to do 

 with a transient tissue re- 

 quires no farther comment 

 after what has been just 

 stated. It ceases to exist 

 when the enamel of the 

 tooth attains maturity. 



In themucoid substance 

 again which enters into 

 the composition of the 

 umbilical cord (fig. 182), 

 namely, the gelatin of 

 Wharton, cells exactly 

 similar to those encoun- 

 tered in the enamel-organ 

 are to be found. 



But this cellular net- 

 work (fig. 182, a) becomes 

 enveloped at a very early 

 period by a clear and deli- 

 cately streaked intermediate substance (b), and in the continuous system of 

 meshes still remaining, we meet with the same structureless mucoid jelly. 

 Here may be found also spherical cells (c) as they appear in the same 

 stage of development of structureless connective-substance. They are 

 contractile, and migrate (Koester). The bands of condensed ground- 

 matter enveloping the cellular net-work (fig. 183, a, b) are subsequently 

 transformed into fibrillse of connective-tissue, and between these there 



Fig. 183. Tissue of the umbilical cord a short time before birth, 

 with well -developed connective-tissue fibrillation, a, b. 

 bands of the latter with their corpuscles in the axis : c, d, e 

 isolated cells. 



