2 Historical Introduction 



saliva secretion occurs (during speech, mastication, the sight and 

 smell of food and in disease) and hinted at a reflex secretion due to 

 irritation of the nerves in the mouth by food. He also noted that the 

 saliva could be observed to emerge from the opening of the parotid 

 duct in little spurts. Haller (1744), who attempted the classification 

 of glandular secretions in his Physiology, suggested that secretion 



Fig. i.i (a), de Graaf's preparation of dogs with pancreatic and salivary 



fistulae. 



(Regner de Graaf, De succo pancreatico, 1677.) 



was due to ultrafiltration from the acini (discovered by Malpighi 

 1683) which he believed to be collections of blood vessels. He sug- 

 gested that an increase in the rate of secretion in a gland was due 

 to increased blood flow and hence an increase in ultrafiltration. 



These views were speculative and the development of a more 

 critical scientific attitude in the early nineteenth century is due 

 largely to the influence of Johannes Muller. Muller wrote a great 

 textbook of physiology which rapidly became the standard work 



