NERVE-TISSUE. 305 



brought to view in a manner far surpassing specimens mounted 

 in balsam. 



Osmic acid (see page 9) may be used successfully. The most 

 important of our present re- agents is the one-half per cent, solu- 

 tion of gold, by means of which J. Cohiiheim * first succeeded in 

 clearing up the termination of nerves in the epifchelia of the 

 cornea. From twenty to forty minutes' exposure to this solution 

 renders all bioplasson formations distinct, although the speci- 

 mens after five or six years become worthless, as they grow too 

 dark for study. Treatment with acetic, lactic, tartaric, and 

 formic acids assists the action of the gold-salt ; but the proper 

 use of these acids can be learned only by experience. 



ANALYSIS OF BIOPLASSON IN ITS RELATIONS TO NERVE-ACTION. 



Thoughtful minds for a number of years have anticipated the modern 

 views concerning the function of the nervous system. I quote from L. 

 Elsberg (I. c., see page 185) the following historical data: 



" According to Drysdale,t Dr. John Fletcher, of Edinburgh, was the first t 

 who clearly abandoned the idea that the material elements of an organism 

 require the addition 'of an immaterial or spiritual essence, substance, or 

 power, general or local, whose presence is the efficient cause of life/ and who 

 arrived at the conclusion that ' it is only in virtue of a specially living matter, 

 universally diffused and intimately interwoven with its texture, that any 

 tissue or part possesses vitality.' He denied vitality to any gaseous or purely 

 liquid fluid, and any hard or rigid solid ; and thought the only truly living 

 matter consisted i of the gray matter of the ganglionic nerves, which he held 

 to be universally diffused, and the gray matter of the brain and spinal mar- 

 row.' He described it as a 'nitrogenous, pulpy, translucent, homogeneous 

 matter, yielding, after death, fibrin.' ' Chemical analysis, accordingly, must 

 be considered as useful in showing us, not what such matter was composed of 

 while it possessed vitality, but what it is composed of afterward.' ' Not only 

 is every vital action traced to molecular change, and to consumption and 

 regeneration of this structureless, semi-fluid matter, combined in a way 

 entirely sui generis, but the initiation of these changes is brought by Fletcher 

 into absolute dependence on stimuli, and all spontaneity or autonomy is 

 denied to matter in the living just as in the dead state.' 



"As Fletcher's work was published in 1835, several years before even 

 the establishment of the cell-doctrine, we cannot but agree so far with Drys- 

 dale as to say that Fletcher has framed a 'hypothesis of the anatomical 

 nature of the living matter which anticipates in a remarkable manner ' its 

 discovery! In 1850, Cohn $ recognized the protoplasm 'as the contractile 



* Virchow's Archiv, Bd. 38. 



t "The Protoplasmic Theory of Life," London, 1874. 

 t " Rudiments of Physiology," Edinburgh, 1835. 



3 "Nachtrage zur Naturgeschic.hte des Protococcus pluvialis." Nova acta Acad. Leop.- 

 Carol., vol. xxii.. part I., p. 605. 



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