574 



MANUAL OF HISTOLOGY. 



\vhich they are enveloped. Large tendons contain in their superficial 

 layers isolated vessels ; while those of greatest magnitude are supplied 

 with blood-vessels as far as their internal Iamina3, while that portion 

 farthest from the surface remains non- vascular. 



The mucous or synovial sheaths of the tendons, vagince synoviales have 

 been already described in speaking of the latter. The synovial sheaths of 

 niiLsdes have also a similar structure, as likewise the biii'scr. mucosce. Most 

 of these are, however, by no means shut serous sacs, as was formerly sup- 

 posed : this is only in some measure the case here and there. The same 

 may be said of the epithelial lining of simple flattened cells ( 87) : it is 

 only met with in portions of the capsules, in the walls of which, further, 

 a sprinkling of cartilage cells may be met with. The contents of all these 

 cavities have been already dealt with in considering the synovia (p. 155). 



In 168 the blood-vessels of the muscles are dealt with, and the 

 nerves of the latter in 182, with the nervous system generally. The 

 lymphatics, as far as we may judge from the scanty observations which 

 have up to the present been made upon the subject, present themselves 

 in muscular tissue in but small number (Teichmann). They were found, 

 however, by Tomsa in the interstitial connective- tissue between the 

 fibres of these organs in the dog : another superficial set, also, is described 

 by His. 



8. Nervous Apparatus. 



291. 



The greater part of the nervous system has already come under con- 

 sideration in an earlier portion of our work ( 174-192): there still 



and spinal cord. 



The medulla spinalis (1), a 

 cylindrical nervous cord, con- 

 sists of an internal grey or 

 greyish-red, and an external 

 white substance. The first, 

 prolonged throughout the 

 whole length of the cord, has, 

 on transverse section of the 

 latter (fig. 553), the shape 

 generally of the letter H; 

 that is, it may be said to con- 

 sist of a middle portion, two 

 anterior (d) and two posterior 

 cornua. The latter, further, 

 are enclosed within another 

 clear gelatinous layer, known 

 as the substantia gelatinosa of 

 Rolando (/). In the middle 

 of the grey substance a deli- 

 cate central canal (c) is ob- 

 served, the only trace left of 

 the rudimentary groove which 



gradually closed in to form the foetal spinal cord. It is lined within by 



ciliated epithelial cells ( 93). 



The circumferential white substance presents deep indentations both 



V 



Fig. 553. Transverse section of the spinal cord of a calf 

 (after Ecker). a, anterior, 6, posterior median fissure; 

 c, central canal; d, anterior, e, posterior cornua; /, sub- 

 xtantia gelatinosa of Rolando; g, anterior column with 

 motor roots; A, lateral column with connective-tissue 

 partitions; t, posterior column with sensitive roots; k, 

 anterior, and Z, posterior transverse commissure. 



