180 THE NERVOUS SYSTEM. 



a short course, 0-09 mm. to 0-35 mm., divides usually about the 

 third constriction (Lenhossek). These processes all pass peripherally, 

 even those which appear at first to pass in the opposite direction 

 curve round again ; it is chiefly due to these fibres that the spinal 

 nerve is larger than its two roots. 



In addition to the above, smaller, irregular cells from 5 jx to 7 /u, 

 in length are found ; Rawitz regards them as young cells, Len- 

 hossek as cells capable of (entwicklungsfahige) developing into 

 nerve-cells. The ganglia contain only few blood-vessels.] 



The above description is founded upon that of Lenhossek, and 

 has been confirmed by the translator in every particular,, except 

 that only very indistinct and unsatisfactory indications of the con- 

 centric fibrillation so clearly delineated by Lenhossek were obtained ; 

 the structure of the Gasserian ganglion was found to correspond 

 exactly with the description here given of the structure of the 

 spinal ganglia. The nucleus was oftener at the side than at the 

 centre of the cell. 



c. The ' Periganglionic Glands ' (Periganglionare Kalkdriisen, 

 v. Lenhossek ; Kalksackchen, Ecker, and others ; Crystal capsules, 

 Wyman; Calcareous Sacs or Masses, of other writers), (Fig. 119). 

 These bodies are found on the ganglia of all the spinal nerves and 

 on the Gasserian ganglion of the trigeminal nerve; they have recently 

 been carefully investigated by v. Lenhossek. According to his 

 description there are usually two to each ganglion, lying on its 

 sides and ventral surface ; each consists of a connective-tissue cap- 

 sule which sends in a few fine trabeculae to support a system of 

 glandular tubes : these usually run parallel to the long axis of the 

 gland, and are about 14 /j. to 15 ^ in diameter; each tube is lined 

 with a single layer of somewhat columnar epithelium, the cells of 

 which have sharp, distinct outlines and oval nuclei. 



A membrana propria was not made out with certainty; the lumen 

 of the tubes is wide and contains a milky fluid, which gives the 

 whole structure its characteristic appearance; it has long been 

 known (Blasius, 1681, mentions the fact, /. c., p. 291) that this fluid 

 contains calcareous matter, which effervesces and dissolves in the 

 presence of hydrochloric acid ; the crystals vary in form but are 

 chiefly oval (Wyman). 



These glands bear no definite proportion to the size of the 

 nerves to which they are attached (Fig. 1 1 8) ; they already contain 

 calcareous matter during the tadpole stage before the limbs are 

 developed (Stannius, Wyman). No ducts have been traced to 



