TISSUES OF THE BODY. 225 



If we turn to a still earlier or embryonic period (fig. 218), wo find 

 in side views (^4) narrow, fusiform, connective-tissue corpuscles without 

 membranes, and with elongated nuclei '01 88-0 '002 3 mm. in length, 

 and O0038 mm. in breadth. These are arranged in longitudinal rows, 

 and are divided from those beside them by narrow deposits of fibrillated 

 intercellular substance measuring about 0-0068-O0045 mm. Transverse 

 sections (B) show, on the other hand, the outlines of the cells contained 

 in irregular roundish or jagged interstices. Thus both views correspond. 



In the adult we find a strongly marked increase in the connective- 

 tissue fibrous matter. The jagged interstices in transverse sections are 

 separated from one another by intervals of 0'0668-0'090 mm. (2). In 

 longitudinal view of the stretched tendon the rows of cells are seen 

 as extremely thin rod-like structures, displaying the greatest diiferences 

 according to the tensity of the tendon (Ranvier). If 'we examine, on 

 the other hand, a tendon in vertical section, no longer on the stretch, 

 but gelatinised and constricted at points by the action of acetic acid 

 (as was formerly done as a rule), we then see narrow twisted structures 

 measuring 0*0451 mm., and reminding us at the first glance of nuclei. 

 These appear to extend themselves into long thin elastic fibres. 



These deceptive appearances were formerly often seen and described. 



But that all tendons contain those flattened cellular elements I doubt 

 very- much from recent investigations. 



REMARKS. 1. The so-called sesamoid cartilages imbedded in certain tendons belong 

 to these. Here we meet with aggregations of cartilage cells generally simple, lying 

 in a ground substance of connective-tissue. 2. If we destroy the interstitial matter 

 formed of connective-tissue by means of concentrated mineral acids, we have 

 remaining a figure corresponding to the cellular network in question. This appears 

 to be the contents of the system of interspaces enclosed in such a modified bounding 

 lamina. For further particulars on this point we must refer to the headings cornea, 

 bone, and dentine. Transverse sections of dried tendons present a very peculiar 

 appearance during the action of acetic acid on them. A number of sinuous band-like 

 figures, namely, appear with fusiform connective-tissue corpuscles and fragments of the 

 most delicate elastic fibres. These are the edges which have turned over on account 

 of the swelling up of the mass, therefore the side view of the sections of the bundles. 



135. 



3. The ligaments have a similar structure to that of tendons, with the 

 exception of those which are elastic. 



4. Fibro- or connective-tissue cartilage^ which might be treated of here 

 with an equal right as when considering cartilage, owing to the nature of 

 its intermediate substance, has been described already with the latter 

 tissue ( 109.) 



5. The large group of fibrous membranes. These are remarkable for 

 the close interweaving of their frequently very strong bundles of connec- 

 tive-tissue, which cross and recross each other. Their elastic elements 

 may correspond to those of the tendons, but are frequently moro 

 numerous, and display a greater breadth of fibre. The proportion of 

 blood-vessels in their composition is but small. Among the fibrous 

 tissues we generally reckon 



a. Such closely-woven whitish envelopes as occur frequently in the 

 form of external coverings to the internal organs of the body. Thus the 

 sclerotica of the eye, with its densely interlacing connective-tissue bundles; 

 the dura mater of the brain and spinal cord, with its numerous elastic 

 fibres ; the fibrous part of the pericardium. Then, again, other fibrous 



