48 CONNECTIVE TISSUE. 



vestigation to swell on the addition of dilute acetic acid,and to become 

 transparent, till they finally altogether disappear ; but they are not 

 actually dissolved even after many hours' exposure to this action, 

 for on washing with pure water, or on neutralising the acid with 

 ammonia, they may be rendered perfectly visible in their original 

 form. As most of the other textural elements which are intermixed 

 with the connective tissue are not similarly affected and rendered 

 invisible by acetic acid, they are brought more distinctly in view 

 by its application ; and hence this agent becomes a valuable aid to 

 the histologist in his study of the tissues. 



The fibres of connective tissue also swell and assume a gela- 

 tinous form in alkalies, but after the prolonged action of the alkali 

 they cannot be again brought to view by the addition of water, 

 being completely dissolved. 



We thus close our remarks on these three groups of tissues, which 

 were all indicated as gelatigenous, even by the older histologists, 

 and in which the most recent investigations have recognized a 

 very surprising analogy. The labours of Virchow,* Donders,f and 

 Kolliker,J have thrown much light upon this subject. Bonders 

 and Virchow especially coincide in this point, that the gelatigenous 

 intercellular substance of these tissues does not originate from 

 cells, but is directly separated from a plastic fluid, while the 

 other elements in these cases (as for instance, in bones, the bone- 

 corpuscles with their prolongations; in cartilage, the cartilage- 

 cells ; and in connective tissue the nuclear or elastic fibres with 

 their nuclei) are primarily formed from cells. Kolliker is also 

 convinced that the nuclear fibres are undoubtedly not formed from 

 the nuclei of the cells of embryonic connective tissue, but from the 

 cell-walls, but he denies that the fibrillae of connective tissue are 

 a direct deposition from the cytoblastema. 



We must not here overlook the fact, which is remarkable in a 

 chemical point of view, that the embryonic connective tissue, accord- 

 ing to Scherer, contains no gelatin, but consists, in addition to 

 fusiform cells, of a peculiar intercellular substance, which on diges- 

 tion with w r ater yields not only albumen, but a gelatinous or mucous 

 substance. Virchow has proposed the term " mucous tissue" for this 

 class of structures, of which the gelatinous substance of Wharton 

 (in the umbilical cord) affords the best example. 



* Verhcindl. d. phys.-med. Ges.zu \Vurzburg. Bd. 2, S. 150 u. 314. 



+ Zeitsch. f. wiss. Zool. Bd. 3, S. 348. 



J Verliandl. d. phys.-med. Ges. zu Wiirzburg. Bd. 3, S. 1. 



