ANATOMICAL CLASSIFICATION OF GLANDULAR ORGANS 275 



sympathetic produces contraction of the vessels of the gland and arrests 

 secretion, while a stimulus applied to the chorda tympani increases the 

 circulation and excites secretion. Enough is known of the nervous 

 influences that modify secretion, to admit of the inference that other 

 glands are supplied with nerves through which certain reflex phenomena 

 affecting their secretions take place. As reflex phenomena involve the 

 action of nerve-centres, it becomes a question to determine whether any 

 particular parts of the central nervous system preside over the various 

 secretions. Experiments showing the existence of such centres are not 

 wanting, but it will be more convenient to treat of these in connection 

 with the physiology of the nervous system. 



Mental emotions, pain and various conditions, the influence of which 

 on secretion has long been observed, operate through the nervous sys- 

 tem. Many familiar instances of this kind may be mentioned : such as 

 the secretion of tears ; arrest or production of the salivary secretions ; 

 sudden arrest of the secretion of the mammary glands from violent 

 emotion ; increase in the secretion of the kidneys or of the intestinal 

 tract from fear or anxiety ; with other examples which it is unnecessary 

 to enumerate. 



Paralytic Secretion by Glands. The effects of destruction of the 

 nerves distributed to the parenchyma of some of the glandular organs 

 are remarkable. If the nerves distributed to the kidney are destroyed, 

 not only is secretion arrested in the great majority of instances, but the 

 renal tissue becomes softened and broken down. After division of tlie 

 nerves of the salivary glands, these organs become atrophied, but they 

 do not undergo the peculiar putrefactive changes observed in the kid- 

 neys. The same effect is produced when the nerves are paralyzed 

 by introducing a few drops of a solution of curare at the origin of the 

 artery distributed to the submaxillary gland. Other glands have so- 

 called motor nerves, stimulation of which excites secretion, but such 

 nerves have been most satisfactorily isolated and studied in connection 

 with the salivary secretions. When the motor nerves of the salivary 

 glands are divided, in the course of a day or two the secretion becomes 

 abundant and watery and loses its normal characters. After about eight 

 days, the secretion begins to diminish and the glands undergo atrophy. 

 The increased secretion first observed is called "paralytic." 



Anatomical Classification of Glandular Organs. The organs which 

 produce the different secretions are susceptible of a classification accord- 

 ing to their anatomical peculiarities, which greatly facilitates their study. 

 They may be divided as follows : 



i. Secreting Membranes. Examples of these are the synovial 

 membranes. 



