THE LACHRYMAL GLAND 219 



As Carlier ('99) and Bensley ('02) have shown in gastric epithe- 

 lium, the cement substance frequently appears on the free sur- 

 face of the cell as a fine irregular network. 



X. CANALICULAR APPARATUS 



It has been shown that many types of cells possess within 

 their cytoplasm very fine anastomosing canaliculi. These were 

 first described by Golgi ('98) in the nerve cells. Later his 

 students, Negri ('00) among others, demonstrated them in 

 many gland cells. Golgi' s silver impregnation method was 

 used for the demonstration of these minute canals. 



Kopsch ('02) showed that they could be demonstrated by 

 long immersion of the tissue in 2 per cent osmic acid. By this 

 method von Bergen ('04) demonstrated the canaliculi in a great 

 many animal cells. 



Holmgren ('02), in a number of papers beginning with 1899, 

 has contributed much to this particular subject, using picric 

 acid-sublimate, toluidin blue and erythrosin method, and later 

 trichloracetic acid and fresh Weigert's resorcin fuchsin. At 

 first Holmgren thought that the canals were lymphatic in nature 

 as he had demonstrated to his own satisfaction that they com- 

 municated with the exterior. Later, mainly as a result of his 

 second technique, he held that these canals (in nerve cells) 

 possessed a network of fibres which had their origin from the 

 nerve capsule. To this network of anastomosing fibres he 

 applied the term spongioplasma and from this developed the 

 well known 'Trophospongium theory.' 



Bensley ('10 b) has shown the analogy of these canaliculi to 

 the vacuoles of plant cells. In the latter (root tip of onion) 

 using formalin bichromate sublimate solution and Kopsch 

 solution as fixatives, he has demonstrated that in the youngest 

 cells the well known vacuoles appear as a canalicular system 

 similar to that in the characteristic animal cell. As the plant 

 cell becomes older the canals enlarge and finally form vacuoles. 

 These were seen by him in the living plant cells, as well. In no 

 instance did he find these canals communicating with the exte- 

 rior. Bensley ('11) describes the canalicuH in both the acinus 



