ELEMENTS OF STRUCTURE. 



101 



transformation of material which goes on in them, although the nature 

 of the processes is only known 

 as regards the striped fibre. In 

 contrast to this, many connective- 

 tissue parts are remarkable for 

 the great permanence of the sub- 

 stances of which they are consti- 

 tuted, especially when they are 

 only scantily supplied with blood- 

 vessels, and possess numerous 

 elastic fibres. In other struc- 

 tures of the same kind a very 

 rapid transmutation of material 

 may take place, when a large 

 amount of blood passes through 

 them, or when they are finely 

 canalised, as for instance, in the 

 case of bone. On the other hand, 

 all connective-tissue structures 

 display an enormous degree of 

 energy 111 a formative direction 

 under conditions of pathological 

 irritation, and are thus of great 

 worth in the plastic processes of 

 the diseased body, considerations 

 which will occupy us again in a 



subsequent section. Fiff 107. Development of nerve-fibres in the frog. 



In regard to the products of transmutation much has been already said. 

 We refer the reader to pp. 21, 

 22 for the glutin-yielding sub- 

 stances ; to pp. 40-50 for the 

 alkaloids. The voluntary or 

 striped muscles, consisting of 

 albuminates, yield as decom- 

 position products, kreatin, krea- 

 tinin, hypoxanthin, inosinicand 

 lactic acids, and inosite. 



Of the physiological decay 

 of the form-elements, and the 

 regeneration and length of exis- 

 tence of the same, we know 

 very little, excepting in the 

 case perhaps of striped muscle- 

 tissue. The duration of many 

 of them, as for instance, of 

 elastic fibres and allied struc- 

 tures, is probably long, for in 

 their case we have only remain- 

 ing the processes of solution 

 and degeneration, mechanical 



attrition beino- excluded (comp. Fi S- 108 -~ Sma11 branching nerve-fibres, a and 6, from the 



. 1-1 /> mesentery of the frog, surrounded by thick envelopes 



p. 94). Ihe three Kinds OI studded with nuclei; 7, the trunk; 2 and 3, the branches. 



transformation, by pigmentation, deposit of fat (fig. 109), and of cal- 



