OHGANS OF THE BODY. 651 



connecting layer of the follicle, and forming, on their part, a net-like 

 covering (c) around the same (b). The most superficial part of this 

 network, namely, that underlying the epithelial layer, runs more or less 

 horizontally beneath the latter, giving off numerous fine terminal twigs of 

 0*0282-0'0113 mm. in diameter, which ascend still farther for a short 

 distance, and then end blind under the epithelial covering. 



The nerves of the conjunctiva (fig. 603, c) terminate, in the first place 

 (as has been shown by Krause), in man and other mammalia in those 

 end-bulbs (a), already described ( 184). Again, as we have learned from 

 Cohnheiiris and Hoyer's interesting discovery, the cornea! nerves extend 

 into the overlying epithelium, or so-called conjunctiva corneae ( 309). 

 For the rest we refer the reader to 184. 



The lachrymal glands, whose sp. gr., according to Krause and Fischer, 

 is 1*058, consist of aggregations of racemose glands, which, as far as the 

 shape of both lobuli and vesicles, and their nucleated cells, composed of 

 finely granular protoplasm, is concerned, present nothing peculiar for 

 our consideration. Their excretory canals, 7 to 10 in number, made up 

 of fibrous tissue lined with columnar epithelium, perforate the conjunc- 

 tiva. In the walls of these we meet again with those flattened stellate 

 cells already alluded to, 194 (fig. 329). The nerves of the organ are 

 supposed to penetrate through the limiting structures of the acini, and 

 terminate between the gland cells in the same manner as in the sub- 

 maxillary gland (Boll). The arrangement of the capillaries here is as 

 usual in such structures. 



The structures composing the apparatus for carrying off the tears are 

 not alike throughout. In the lachrymal canals the tissue of the mucosa 

 is rich in elastic fibres, while in the lachrymal sac and duct a reticulated 

 connective substance, containing lymphoid cells, presents itself (Henle). 

 From the lining membrane of the nose small mucous glands extend 

 upwards, and occur not only in the wide nasal duct, but also in the 

 mueosa of the canaliculi (R. Maier). In regard to the species of epithe- 

 lium lining the lachrymal passages there still exists much diversity of 

 opinion. Non-ciliated columnar cells are stated to occur throughout 

 them by Maier. Henle, on the other hand, mentions having found 

 flattened epithelium in the canaliculi, ciliated in the lachrymal sac and 

 nasal duct, merging into the flattened formation of the nose. 



We turn now to the tears, the secretion of the lachrymal glands, which, 

 with a small quantity of aqueous humour, which exudes through the 

 cornea, bathe the front of the eye. This fluid has a strong alkaline 

 reaction and slightly saltish taste. Chemical analysis, instituted long 

 ago by Frericlis, shows about 1 per cent of solid matters (0*9-1 '3 per cent.) 

 Among these albumen appears in combination with soda (the " lachry- 

 mirie " of earlier investigators), together with traces of fats, extractives, 

 and mineral matters. Of the last chloride of sodium is the most import- 

 ant, phosphates of the alkalies and earths appearing in but small amount. 

 Under ordinary circumstances the tears are carried off by the canaliculi 

 into the nose, but when the secretion is too abundant it overflows the 

 lower lid. The psychical significance in the human being of tears has 

 long been recognised. 



321. 



The development of the eye, to which we will only devote a few words 

 tere, takes place from three different portions of the rudimentary embry- 



