REFLEX SECRETION OF SALIVA. 489 



submaxillary saliva. And it happens that the ducts with striated 

 epithelium are very scanty in the sublingual gland, whilst they are 

 numerous in the submaxillary gland. 



EEFLEX SECRETION OF SALIVA IN NORMAL AND IN OTHER 

 CONDITIONS. 



In man, more complete observations have been made on the flow 

 of saliva from the parotid than on that from the submaxillary gland, 

 since the duct of the parotid is sometimes accidentally injured, so that 

 the establishment of a parotid fistula becomes necessary. But some of 

 the conditions of flow from either gland may be readily observed, when 

 a cannula is simply placed in the opening of the duct of the gland into 

 the mouth. 



In the dog, sheep, horse, and other animals, sometimes a permanent 

 fistula, and sometimes a temporary fistula, of one or more of the glands 

 is established. The observations have been made with and without the 

 administration of anaesthetics. 



Ordinarily, between meals, the large salivary glands except the 

 parotid glands of ruminants do not secrete. But as the mucous 

 membrane of the mouth is constantly kept moist, saliva must constantly 

 be formed by the smaller glands of the mucous membrane. In some 

 animals the amount of this secretion is very considerable ; thus in the 

 horse, during abstinence, 100 to 150 c.c. of saliva are, according to Colin, 1 

 formed in an hour. Probably during sleep the amount diminishes. 

 There is little doubt that this secretion is produced reflexly by conditions 

 affecting the mucous membrane of the mouth, and a slight increase in 

 the strength of the stimuli probably sets in action the larger glands also. 



In ruminants there are some peculiarities. The parotid gland se- 

 cretes continuously (Colin, 1 Eckhard 2 ). The secretion is most abundant 

 during feeding, rather less during rumination, and one-eighth to one- 

 fourth the rumination rate during rest. 1 During rest, the submaxillary 

 glands secrete little or not at all, and it is a remarkable fact that 

 rumination does not, as a rule, cause any secretion from these glands, 

 although it increases the secretion from the parotid gland, and although 

 feeding causes a secretion from all the glands. 



Colin found in ruminants a slight continuous secretion from the sub- 

 maxillary and sublingual glands during rest. Ellenberger and Hofmeister 3 

 found none, but they noticed that there was occasionally a slight secretion 

 from the submaxillary gland during rumination, and a more copious secretion 

 during the act of drinking. According to these observers, there are occasional 

 short pauses in the parotid secretion during rest. 



In ruminants, further, it has been said 4 that the secretion from the parotid 

 gland continues after section of all the nerves running to it. In the ox, 

 Moussu (1890) found that section of the buccal nerves diminished greatly, 

 but did not quite stop, the parotid secretion. Eckhard (1893) states that 

 section of these nerves does not affect the parotid secretion in the sheep ; he 

 found about 1J c.c. to be secreted in ten minutes, whether the nerves were 

 cut or no. The matter requires further investigation. 



1 Op. cit. 2 ztschr.f. rat. Med., 1867, Bd. xxix. S. 74. 



3 Arch.f. Anat. u. Physiol., Leipzig, 1887, Physiol. Abth., Supp. Bd. S. 138. 



4 Centralbl. f. Physiol., Leipzig u. Wien, 1893, S. 365. Cf. Schwann, Beitr. s. Anat. 

 u. Physiol. (Eckhard}, Giessen, Bd. vii. S. 170. 



