146 CONNECTIVE TISSUE. 



conditions, is an excellent means to render the reticulum in the basis- 

 substance of cartilage visible, without any re-agent. In ground specimens 

 of dry bone the cavities (lacunas) and their offshoots (the canaliculi) are very 

 marked, especially if filled with air or other extraneous matter, because the 

 difference in the refraction of the calcified basis-substance and the cavities, 

 deprived of their bioplasson, is very great. The more the lime-salts are 

 extracted from the basis-substance f. i., by a solution of chromic acid, 

 which at the same time preserves the bioplasson the less visible are the 

 cavities and their offshoots. A small amount of lime-salts, left behind even 

 after chromic-acid treatment, renders both cavities and canaliculi, both the 

 bone-corpuscles and their offshoots, plainly visible. 



The development of basis-substance invariably takes place 

 from the bioplasson liquid. Either single plastids are infiltrated 

 with basis-substance and rendered pale, apparently structureless, 

 or the process takes place in a number of coalesced plastids, from 

 which the formation of a territory results. Within this territory 

 unchanged plastids are left, the connective-tissue corpuscles 

 proper. The first manner of formation of basis-substance occurs 

 in the simplest and earliest varieties of myxomatous connective 

 tissue, the latter manner in all higher developed forms of 

 fibrous, cartilaginous, and bony connective tissue. 



(1) Myxomatous or Mucoid Tissue. Myxomatous tissue is the 

 earliest connective-tissue formation in the embryo, and all later 

 varieties of connective tissue arise from this. As soon as the 

 mesoblast is produced, we recognize it by the presence of numer- 

 ous plastids, uniform in size and shape, some homogeneous, 

 others granular and nucleated. All are connected by means of 

 delicate filaments, traversing the light rim around each plastid. 

 This tissue is called the embryonal or indifferent tissue, the latter 

 term meaning that no difference can be discovered in the char- 

 acter of the plastids. 



During the first few weeks of embryonal life we meet with 

 myxomatous connective tissue only, and also during the entire 

 period of intra-uterine development this kind of tissue largely pre- 

 vails ; it also forms the tissues destined for the attachment of the 

 embryo to the womb and for its nutrition, viz. : the placenta and 

 the umbilical cord. With advancing development of the body 

 the myxomatous tissue is replaced by more advanced formations, 

 and in the full-grown individual only the vitreous body of the eye 

 exhibits features similar to those of the umbilical cord (Virchow). 

 We also meet with it in all remnants of embryonal development, 

 such as medulla of bone, adenoid or lymph-tissue (lymph- ganglia, 

 spleen, submucous adenoid layers), and tooth-pulp. 



