232 ALFRED SANGSTER. 



darkness and in red and yellow light, the retina as far as the 

 layer of rods, may be almost always stripped off as a contin- 

 uous membrane free from retinal pigment (the processes of 

 the pigment cells being retracted from it), this by no means 

 takes place so smoothly in the decolourised retina ; the retina 

 commonly tears into several shreds to which larger or smaller 

 quantities of retinal pigment remain inseparably attached. 



III. I have not rashly ascribed the various actions of the 

 separate regions of the spectrum to the different wave- 

 lengths of the rays, and have omitted the obvious reference 

 to the stronger chemical action of the short-waved rays, 

 because experiments on the operation of the ultra-violet rays 

 on the colour of the retina have yielded only negative 

 results. 



Observations o?i the Muscular Coat of Sweat-glands. 

 By Alfred Sangster, M.B. Cantab. (With Plate XVII.) 



It has loner been known that some of the sweat-glands of 

 the human subject possess a muscular coat. Kolliker in his 

 treatise on Histology says — 



" The canals of glands (sweat) have either thick or thin 

 walls. The latter possess a covering of indistinctly fibrous 

 connective tissue, with elongated scattered nuclei which is 

 sharply bounded internally by a delicate membrana propria, 

 and this is lined by a simple double or multiple layer of 

 polygonal cells. The thick-walled sudoriparous glandular 

 canals have in addition to the two coats above described a 

 middle layer of longitudinal smooth muscular fibres whose 

 elements are readily separable." Concerning the ceruminous 

 glands the same author remarks : — " In their intimate struc- 

 ture ceruminous glands are constituted as follows : — The tube 

 of the glandular coil possesses a fibrous coat and an epithe- 

 lium. The fibrous coat possesses exactly the same characters 

 as that of the larger sudoriparous glands, i.e., it consists of 

 an internal layer of smooth muscular tissue disposed longi- 

 tudinally and of an external layer of connective tissue with 

 scattered nuclei and occasionally very fine transverse elastic 

 fibres. The epithelium lies probably on a membrana 

 propria, and consists of a simple layer of polygonal cells 

 which contain yellow-brown pigment cells." 



