TISSUES, ORGANS, AND SYSTEMS. 



83 



Fig. 26. 



Fig. 27. 



solved: nitric acid colors them yellow; Millon's test* for protein tinges 

 them red ; whilst sulphuric acidf and sugar have no action (red colora- 

 tion) upon them. In a moderately diluted solution of potassa, elastic 

 tissue remains, for a long time, unaltered in the cold, except that it 

 swells up and becomes somewhat paler. Heated for a day with it, it 

 becomes converted into a gelatinous mass. In water this tissue does 

 not alter, even after sixty hours' boiling, but changes by boiling for 

 thirty hours in Papin's digester into a brownish substance, smelling like 

 glue, but not gelatinizing, which is precipitated by tannic acid, tincture 

 of iodine, and corrosive sublimate, but not by the other tests for chondrin. 

 Physiologically, the prominent characteristic of this tissue is its elas- 

 ticity, in consequence of which it forms a most essential support to the 

 motor organs, and also plays an im- 

 portant part in other situations, e. g. 

 in the vocal ligaments. With respect 

 to its development, the supposition of 

 Schwann, that this tissue proceeds 

 from cells, receives increasing support 

 from modern investigations ; in fact, 

 in all those organs which subsequently 

 contain elastic tissue, there may be 

 discovered in embryos, peculiar fusi- 

 form or stellate, sharply-pointed cells, 

 which by their coalescence produce 

 long fibres or reticulations, in which 

 at first, those localities where the 

 bodies of the cells previously existed 

 may still be recognized as enlarge- 

 ments containing elongated nuclei in 

 their interior. In this condition the 

 fibres not unfrequently remain, and 

 they then form a modification of what 

 were formerly called nucleus-fibres , or 

 every trace of their previous composi- 



FiG. 26. Formative cells of the elastic fibres, from the tendo-Achillis : a, of a four months' 

 embryo ; 6, from a seven months' foetus, a few cells free, with one and two processes, 

 others united by twos and threes. Magnified 350 diameters. 



FIG. 27. Stellate formative cells of the nucleus-fibres out of the tendo-Achillis of a new- 

 born infant. Magnified 350 diameters. 



by rendering the latter transparent, permits us to investigate the former. In preparations 

 thus treated the subsequent addition of ammonia, by neutralizing the acid, causes the fibres 

 of the connective tissue to reappear, and those of the elastic tissue to recede. DaC.] 



* [Millon's test (see Compt. Rend. t. 27, p. 42-44), is the most delicate test for protein 

 known. It consists in heating the suspected fluid or tissue from 60 to 100 in a solution 

 of one part of mercury, in two parts of nitric acid. If protein be present an intense red; 

 color results, which does not disappear on prolonged boiling. DaC.]] 



t [The immediate effect of sulphuric acid is to render the fibres more distinct. DaC.] 



