INS ALI VATION. 157 



taken from the duct of Steno. 1 Numerous opportunities have 

 presented themselves, in cases of salivary fistula, for the study 

 of the properties of the pure parotid saliva in the human 

 subject; and the situation of the duct of Steno, in the her- 

 bivora especially, is such that this fluid can easily be obtained 

 by operations on the inferior animals. Prof. Dalton has 

 obtained the pure parotid saliva from the human subject by 

 simply introducing a silver tube, of from ^j to -jV of an inch 

 in diameter, into the duct by its opening into the mouth. 2 In 

 this way the fluid may be obtained with great facility and in 

 absolute purity ; and by this means, Prof. Dalton has devel- 

 oped many interesting facts connected with its function, be- 

 side confirming some of the important observations of Ber- 

 nard, Colin, and others, on the inferior animals. The quan- 

 tity thus obtained was considerable. In one observation, 

 four hundred and eighty grains flowed from a tube intro- 

 duced into the duct of Steno in the course of twenty min- 

 utes ; and in seven successive observations, made on different 

 days, comprising in all three hours and nine minutes, a little 

 over three thousand grains were collected. 3 



1 TIEDEMANX ET GMELiN, Redierches Experimentales Physiologiques et Chi- 

 miques sur la Digestion, traduit par JOURDAN, Paris, 1827, tome i., p. 4 et seq. 



2 DALTOX, A Treatise on Human Physiology, third edition, Philadelphia, 

 1864, p. 125 et seq. 



3 The saliva thus obtained was analyzed under the direction of Prof. Dalton 

 by Mr. Maurice Perkins, Assistant to the Professor of Chemistry in the College 

 of Physicians and Surgeons, New York (op. cit., p. 126). A point to be re- 

 marked in this analysis is the large proportion of organic matter, which is sev- 

 eral times greater than that given by others for the parotid, or even for the mixed 

 saliva : 



Composition of Human Parotid Saliva. 



Water 983-308 



Organic matter precipitable by alcohol 7 '352 



Substances destructible by heat, but not precipitated by alcohol or acids 4-810 



Sulpho-cyanide of sodium 0-330 



Phosphate of lime 0-240 



Chloride of potassium 0-900 



Chloride of sodium and carbonate of soda 3-060 



1,000-000 



