ELEMENTS OF STRUCTURE. 



87 



Fig. 84. Fibro-reticular cartilage 

 from the human epiglottis. 



Chemically, intercellular substance may either appear as a fluid con- 

 taining albuminous matters in solution (blood, lymph), or as a jelly com- 

 posed of gelatinised protein compounds (many 

 fcetal tissues), or as coagulated metamorphosed 

 albuminous substances (epidermis, nails), or as 

 glutin-yielding tissue, such as chondrin (in per- 

 manent cartilage), or finally as elastic material 

 (in elastic or yellow cartilage). 



Now, by ScJiwann this intercellular substance 

 was regarded as the primary structure in which 

 he supposed the cells subsequently to take their 

 origin, a view which was favoured for a very 

 long time by the greater number of histologists. 

 The fact, however, that in the earlier periods of foetal life no intercellular 

 substance is found between the cells of growing tissue, seems to point to 

 another conclusion (especially when viewed in the light of present-day 

 science), namely, that the matrix is a product of the secretion of the cell 

 itself, or a metamorphosed peripheral portion of the cell-body, the con- 

 tribution of each element fusing, of course, into the common mass. 



And, indeed, there are appearances in cartilage which admit of no other 

 explanation. Thus, we not unfrequently remark that the peripheral 

 capsular layers surrounding the cells like a halo, blend into the adjacent 

 intercellular substance without any sharp line of demarcation. But the 

 appearances presented by sections of cartilage which 

 have been treated with certain reagents are of far 

 greater importance even (fig. 85). Here the ap- 

 parently homogenous matrix of fig. 83, for instance, 

 is resolved into systems of thick capsules, which en- 

 circle the various cartilage cells, or groups of the 

 latter touching each other at their circumference. 

 We shall refer to this again further on. 



But if blood, lymph, and chyle be numbered 

 among the tissues of the body which may be rea- 

 sonably done their fluid intercellular substance is 

 certainly of other origin, i.e, not produced by the 

 corpuscles. The cellular elements of lymph have rather wandered 

 actively out of the lymphatic glands in part, and have been partly carried 

 out with the currents of the fluid, just as a stream may sweep away por- 

 tions of its banks, and transport them to a greater or less distance. 



54. 



In a former section we have already considered the question, how far 

 the growth of parts depends upon a simple enlargement of cells already 

 present, and how far upon an increase in the number of the cellular 

 elements of which the part is composed. "We have seen that the last- 

 named mode of growth is the rule: cellular structures increasing in 

 volume, usually show a multiplication of their elements. The cell, like 

 all organic formations, is a transient structure, and in all probability 

 invariably endowed with a term of existence far shorter than that of the 

 body generally, and which may be named in many cases exceedingly 

 brief when compared with the latter. It stands to reason, then, that it 

 must either possess the capability of proliferation, of reproducing similar 

 structures to itself, of generating a progeny, or whole families of co'ls 

 7 



Fig. 85. Thyroid cartilage 

 of the pig treated with 

 bichromate of potash and 

 nitric acid. 



