170 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



later observers, however, the mucous cells do not actually disintegrate, but 

 form again new material during the period of rest as was described for the 

 goblet cells of the intestine. In the mucous as in the albuminous cells ob- 

 servations upon pieces of the fresh gland seem to give more reliable results 

 than those upon preserved specimens. Langley l has shown that in the fresh 

 mucous cells of the submaxillary gland numerous large granules may be 

 discovered, about 125 to 250 to a cell. These granules are comparable to 

 those found in the goblet cells, and may be interpreted as consisting of 

 mucin or some preparatory material from which mucin is formed. The 

 granules are sensitive to reagents ; addition of water causes them to swell up 

 and disappear. It may be assumed that this happens during secretion, the gran- 

 ules becoming converted to a mucin-mass which is extruded from the cell. 



Action of Atropin, Pilocarpin, and Nicotin upon the Secretory 

 Nerves. The action of drugs upon the salivary glands and their secretions 

 belongs properly to pharmacology, but the effects of the three drugs men- 

 tioned are so decided that they have a peculiar physiological interest. Atro- 

 pin in small doses injected either into the blood or into the gland-duct 

 prevents the action of the cerebral fibres (tympanic nerve or chorda tympani) 

 upon the glands. This effect may be explained by assuming that the atropin 

 paralyzes the endings of the cerebral fibres in the glands. That it does not 

 act directly upon the gland-cells themselves seems to be assured by the inter- 

 esting fact that with doses sufficient to throw out entirely the secreting action 

 of the cerebral fibres, the sympathetic fibres are still effective when stimulated. 

 Pilocarpin has directly the opposite effect to atropin. In minimal doses it 

 sets up a continuous secretion of saliva, which may be explained upon the 

 supposition that it stimulates the endings of the secretory fibres in the gland. 

 Within certain limits these drugs antagonize each other that is, the effect of 

 pilocarpin may be removed by the subsequent application of atropin and vice 

 versa. Nicotin, according to the experiments of Langley, 2 prevents the action 

 of the secretory nerves, not by action on the gland-cells or the endings of the 

 nerve-fibres, but by paralyzing the nerve-ganglion cells through which the 

 fibres pass on their way to the gland. If, for example, the superior cervical 

 ganglion is painted with a solution of nicotin, stimulation of the cervical 

 sympathetic below the gland will give no secretion ; stimulation, however, of 

 the fibres in the ganglion or between the ganglion and gland will give the 

 usual effect. By the use of this drug Langley is led to believe that the cells 

 of the so-called submaxillary ganglion are really intercalated in the course 

 of the fibres to the sublingual gland, while the nerve-cells with which the 

 submaxillary fibres make connection are found chiefly in the hilus of the 

 gland itself. 



Paralytic Secretion. A remarkable phenomenon in connection with the 

 salivary glands is the so-called paralytic secretion. It has been known for a 

 long time that if the chorda tympani is cut the submaxillary gland after a cer- 



1 Journal of Physiology, 1889, vol. x. p. 433. 



2 Proceedings of the Royal Society, London, 1889, vol. xlvi. p. 423. 



