TISSUES OF THE BODY. 189 



similar to it, and which is thus distinguished from glutin-yielding car- 

 tilage and regular connective-tissue. The amount of this interstitial 

 substance is usually considerable, so that all the physical properties of 

 the tissue are determined by it. In this respect cartilage and gelatinous 

 tissue resemble each other, though, on. the other hand, they may differ 

 widely as regards consistence. 



The cells in a soft interstitial substance of this kind are originally 

 of spheroidal figure, and when imbedded in a completely homogeneous 

 mass may be regarded as the simplest form of gelatinous tissue one 

 which is, however, but extremely rarely permanent, and which is 

 destined to undergo, as a rule, further transformation, fhe cells, in 

 such cases, are metamorphosed into fusiform and stellate structures, 

 displaying a strong inclination to unite with one another, and in the 

 intercellular substance there commences to make its appearance a streaki- 

 ness and fibrillation. 



In general, mucoid tissue may be said to be a species of connective- 

 substance standing low in the group, and as such it enters into the com- 

 position of temporary embryonic structures under normal conditions, 

 which do not attain in this form a state of maturity. In fact, we have 

 to do with foetal tissues. The cells further, while still in their simplest 

 form, may be so compressed by the superabundant interstitial matter 

 that they cease to exist, the latter only remaining over. It is, how- 

 ever, more usual to meet with an ascending metamorphosis in other of 

 these textures, by which they are developed into ordinary soft connec- 

 tive-tissue. The points of distinction, consequently, between the two 

 cannot be very definitely laid down. 



The parts of the human body which are looked upon at the present 

 day as belonging to this group of tissues are the following : the vit- 

 reous humour of the eye ; the gelatin of Wharton of an early period of 

 life \ certain substances filling up the interior of the rudimentary ear ; 

 the enamel organ of the rudimentary teeth ; and the soft, formless con- 

 nective-tissue of intra-uterme life, which has not yet developed collagen. 

 But in animals gelatinous tissue is more permanent. Thus the sinus 

 rhomboidalis in the spinal cord of birds is formed of it, and the form- 

 less connective -matter of fishes. It appears also widely distributed among 

 the lower animals. The bodies of the acalephse are chiefly made up of it 

 (Virchow and Schultze). 



Whilst in the mature body no gelatinous tissue is to be found, with 

 the exception of that small quantity known as the vitreous humour, it 

 may be produced anew under abnormal conditions by development from, 

 another member of the group of connective-tissues, as, for instance, from 

 fatty tissue in cases of emaciation. Tumours formed of mucoid tissue 

 are known as myxomas ( Virchow). 



115. 



The simplest form of this gelatinous tissue to be found is in the corpus 

 vitreum of the eyes of embryos and very young individuals. 



The surface of the latter is originally covered with a vascular net- 

 work, which is obliterated, however, very early. If we examine the 

 structure in a fcetus at about the end of the fourth month (fig. 180), 

 we find it to consist of an abundant and completely colourless, homo- 

 geneous, and somewhat viscid ground-substance, which becomes stringy 

 on the addition of acetic acid. In this are imbedded, at tolerably 



