CHAPTER II 



THE MINUTE STRUCTURE OF THE NERVOUS 



TISSUES 



OUR Introduction began with references to the existence 

 of a few types of tissue ill the human body. These types 

 have been familiar to anatomists for more than a century. 

 A large share of the credit for their recognition and 

 definition belongs to Bichat, a French worker, whose 

 short life of only thirty years (1771-1801) was extra- 

 ordinary for the extent of its achievements. Forty years 

 after the death of liichat an important step had been 

 taken toward a more comprehensive knowledge of the 

 way in which living matter is constructed. The doe- 

 trine declared at that time is known as the Cell Theory. 

 Its establishment was directly due to a noteworthy im- 

 provement in the lenses made for microscopes. 



The Cell Theory is to the effect that all forms of life can 

 be demonstrated to exist as single or associated units of a 

 certain standard kind. These units of structure continue 

 to bear the name of cells, though the word became fixed 

 upon them at first as the result of a misconception. It 

 i- not logical to use a word which properly means a cavity 

 to stand for a more or less solid mass of material, but this 

 is the actual practice. The biologic cell may be regarded 

 as having the same relation to a cell in the precise sense 

 of the term that a cast has to the mold. In short, the cell 

 is a small parcel of living matter, the smallest which can 

 continue long to have the behavior which we associate 

 with the living state. 



An average cell is microscopic in si/e. Many of those 

 in t he body would be found to measure less t hail , ' inch 

 in diameter; the red corpuscles of the blood, for example, 



