FINE NERVE-FIBRES COMPOUND. 171 



nervous system resembles the active part of the 

 nerve-fibre in the higher animals, especially at an 

 early period of development. The active part of the 

 nerve-fibre in adult vertebrata invariably consists of 

 a very delicate compound thread which exhibits a 

 slightly fibrous character, and is composed of an oleo- 

 albuminous material. Connected with the threads at 

 vary ing intervals are oval masses of bioplasm. Inhighly 

 sensitive peripheral nerve-organs, and in the motor 

 nerves of muscle, these masses of bioplasm are very 

 numerous, and, in some cases, are almost continuous 

 with one another ; but in less sensitive textures the 

 masses of bioplasm are often separated from one 

 another by a distance of T o-th of an inch or more. 

 In all cases these bioplasts or " nuclei " are situated 

 very close together at an early period of develop- 

 ment, and at first the tissue which represents nerve 

 consists of bioplasm only. As the tissue advances 

 towards maturity, the masses of bioplasm become 

 gradually separated from one another by a greater 

 extent of fibre, but at all periods of life and in all 

 peripheral branches of nerves these bodies are present. 

 23 O. Fine nerve-fibres compound. The fine nerve- 

 fibre sometimes appears as a very distinct fibrous 

 structure, which, were it not actually traced to un- 

 questionable nerve- fibres, might be easily mistaken 

 for fibrous or connective tissue ; sometimes as a very 

 delicate expansion of such extreme tenuity as to be 

 demonstrable only after it has been partially altered 

 by chemical reagents, and the oily matter separated 

 from it in the form of granules or globules, which 

 can be very easily traced. Fibres often pass off at an 

 angle from these fine nerve-fibres, and divide and sub- 

 divide, joining others, so as to form a network, the 

 meshes of which vary much in diameter in different 

 cases. Every one of these delicate fibres of which 

 some are not more than the -rc^oiro ^ an i ncn i n 

 diameter, must be regarded as composed of still 



