418 Dr. R. D. Thomson on the Digestion of 



is evidently reduced ultimately in theory (Phil. Mag,, Febru- 

 ary, p. J 66*), as in experiment (Phil. Mag., April, p. 331 1)» 

 to admit that the central parts slide past the lateral parts, from^ 

 whatever cause, and thence derive their superior rapidity of 

 motion. 



I have now^ entered more fully into this controversy than I 

 at first intended ; and as I do not think it likely that Mr. 

 Hopkins can meet me on anything like new ground on this 

 subject, I wish to decline any merely polemical writing. Any 

 further explanations I have to give will, therefore, be con- 

 tained in memoirs of the ordinary form and not controversial 

 in their tendency. 



Edinburgh, April 16, ] 845. 



LVIII. On the Digestion of Vegetable Albumen, Fat and 

 Starch. By Robert D. Thomson, M.D., Lecturer on 

 Practical Chemistry in the University of Glasgow. 

 [Continued from p. 328.] 

 "D EING thus foiled in corroborating the deduction of Blond- 

 *-' lot, that phosphoric is the free acid of the stomach, it was 

 requisite to look out for another source of the acidity of the 

 gastric fluid. It was therefore necessary to test the muriatic 

 or hydrochloric acid theory, as propounded by the sagacity 

 of Dr. ProutJ. 



The contents of the stomach of a pig which had been fed 

 on porridge two hours before being killed, were mixed with 

 cold distilled water and filtered. Six fluid ounces of this fluid, 

 which was quite clear and limpid, were introduced into a re- 

 tort and distilled in a water-bath. The distillation occupied 

 several hours ; three ounces of fluid were distilled over, which 

 possessed the peculiar smell of such fluids, and reddened in- 

 fusion of litmus slightly. The three ounces of fluid remaining 

 in the retort had a strongly acid reaction, and gave no ap- 

 pearance of acetic acid on the addition of chloride of iron. 

 From twelve ounces of another portion of the same gastric 

 fluid, four ounces of fluid were distilled over by the heat of 

 the water-bath, which presented the same characters as those 



* " I have no doubt that the first fractures would be transversal, pro- 

 duced by the tension (R) ; and that after the mass had thus become consi- 

 derably dislocated along its sides, the sliding of one finite portion past an- 

 other would also take place." 



\ "When the central motion was continued long enough, the fissures 

 along the flanks became more irregular and ran into each other, after which 

 the central portion moved nearly as a continuous mass, sliding past the 

 narrow lateral portions, from which it was severed on either side by the 

 lateral fissures running into each other as just described." 



X See Phil. Mag. S. 2. vol. iv. p. 3. and 120. 



