360 SPECIAL ANATOMY. 



themselves, are, like the capillaries, variable, according to the 

 organs into which they enter. 



In the contractile tissues (muscles, and so forth), the nerves are 

 said (by C. Burdach) to terminate with narrow loops, in the parts 

 endowed with sensation (the skin, organs of the senses, &c.), with 

 plexuses and wide loops. 



Moreover, each single muscular fibre and cell of an organ is 

 not pervaded by a corresponding nerve fibre. 



4. The vessels (capillary and lymphatic) of the nerves are dis- 

 persed in their neurilemma. 



[Pacinian bodies, corpuscles. Observed by Pacini in 1831. 

 " Small corpuscles or globules, of an elliptical figure to the 

 eye, dull white or opalescent, of about two-thirds of a line long, 

 lying attached to the digital branches of the median and ulnar 

 nerves." They are also found along the nerves of the sole of the 

 foot. See the article in Cycl. of Anat. and Physiol,]. 



613. The Central parts, 



brain and spinal cord, consist of the same elements as the peri- 

 pheral. The primitive fibres and ganglion globules are accumu- 

 lated in masses, and united into definite shapes, which are not 

 separated from one another by means of external sheaths. 



The white substance consists of fasciculi of primitive fibres 

 which are continued from the nerves, interlace, decussate, and 

 either pass through the gray substance of the central organs or 

 receive it between them. According to Valentin there are, even 

 here, no terminations to the nerves; but, as in the peripheral, 

 only places for their reflection ; so that every primitive fibre is 

 closed in a circular manner, and by that it might be decided that 

 in the central organs no other fibres exist as such which continue 

 into the nerves. 



The gray substance exists under different colours, partly as ex- 

 ternal (the cortex of the brain), partly as internal (in the spinal 

 marrow) masses, in the deep layers of which (in the brain) fibres 

 are also found, together with the ganglion globules (Lautb). 



1. The spinal cord sends off from thirty-one to thirty-two nerves 

 upon either side, the posterior roots of which are subservient to 

 sensation, those of the anterior to motion. Higher upwards the 

 fibres of these roots decussate in the medulla oblongata, as the 

 right pass off to the left, and the reverse. From this point (almost) 

 all the fibres pass upwards into the brain through Pans Varolii in 

 the crura cerebri, and partly into the cerebellum. 



According to Budge, the spinal cord contains motor fibres in its 



