CoGHiLL, Structure of the Nerve Cell. 185 



HoLM(iREN ('99, '00) asserts that the canaliculus is continuous 

 with the pericellular lymph space and that it is accompanied by trabe- 

 culae of the connective tissue capsule of the cell. Along with it occur 

 also the nuclei of its membranous walls and connective tissue nuclei 

 which have migrated in from the capsule of the cell, while corpuscles 

 of the lymph circulate through the canaliculus. 



KoLSTF.R ('00) observes canaliculi also in the nerve cell of the 

 spinal cord and spinal ganglia of Pctromyzon . He has demonstrated 

 them successfully in unstained sections of cells fixed in osmic acid. 

 He traces them from the periphery of the cell into the deepest part 

 where they seem to be continuous with a perinuclear space of the same 

 nature. A slight invagination of the endothelial capsule may occur 

 where the canaliculus enters the cell and free nuclei are found in the 

 protoplasm which are interpreted as nuclei of the capsule ; but KoL- 

 STER. even with the technique employed by Holmgren, fails to find a 

 nucleated membranous wall surrounding the lumen of the canaliculus. 

 It is bordered simply by the granular protoplasm of the cell. Still, in 

 a later work, Holmgren ('00) confirms his first observations by dem- 

 onstrations of the canaliculus in the nerve cells of mammals and birds 

 with all the features originally described for Lophiiis. He further 

 shows that electrical stimulation of tlie nerve cell causes an expansion 

 of the canaliculi. 



Holmgren's interpretation of the canaliculi receives positive sup- 

 port from the observations of Pugnat ('01) upon the embryological 

 development of the canaliculus in the nerve cell of the chick. Pugnat 

 finds that the canaliculi appear first in the outer zone of the spinal 

 ganglion cell on the eleventh day. By the fifteenth day they have 

 reached the central zone. These canaliculi, according to Pugnat also, 

 have membranous walls and are continuous with extracellular vessels 

 of the same nature. 



Canaliculi have been recognized also by Bochenek in the largest 

 nerve cells of Helix. As to the structural and topographical features 

 of the system, Bochenek agrees in the main with Holmgren. He 

 finds the connective tissue fibrillae and cells very conspicuous in the 

 protoplasm of the nerve cell and even invading the basal portion of the 

 axone. He explains the structure as a simple invagination of the cap- 

 sule into the body of the nerve cell or as clefts in the cell. His fig- 

 ures and descriptions would not give one the idea of a clearly defined 

 membranous wall about these clefts, yet he says "Si, dans cet expose 

 des faits, nous sommes en complet accord avec le travail de Holm- 



