56 GASTRIC JUICE. 



the gelatigenous tissues as perfectly identical. The following pro- 

 perties, which Mialhe attributes to his albuminose, are certainly 

 correctly observed, and are common to most of the peptones ; in 

 the solid state the digested substances are white or of a pale 

 yellow colour, possess little taste or odour, and dissolve readily in 

 water and slightly in spirit, but not at all in absolute alcohol. 

 The watery solutions of these substances are not precipitated by 

 boiling, by acids, or by alkalies, but deposits are thrown down by 

 metallic salts, by chlorine, and by tannic acid. 



My own observations lead me to the belief that all the pep- 

 tones are white, amorphous bodies, devoid of any odour, and 

 having merely a mucous taste, soluble in every proportion in 

 water, and insoluble in alcohol of 83^; their watery solutions 

 redden litmus ; they combine readily with bases with alkalies as 

 well as with earths so as to form neutral salts, which are very 

 soluble in water. The aqueous solutions of these salts are only 

 precipitated by tannic acid, corrosive sublimate, and, if caustic 

 ammonia has been previously added, by acetate of lead; all other 

 metallic salts, even nitrate of silver and alum, produce no preci- 

 pitate, and even basic acetate of lead only induces a slight turbidity, 

 which disappears on the addition of an excess of the test. No 

 precipitation or turbidity is produced by the addition of mineral or 

 organic acids, either in a concentrated or in a very dilute state ; 

 even chromic acid fails to produce any appreciable effect. The 

 ferrocyanide and ferridcyanide of potassium, when added to solu- 

 tions acidified with acetic acid, occasion only a slight turbidity. 



I have been unable to obtain the peptones perfectly free 

 from mineral substances : I have, however, obtained them free 

 from phosphates and hydrochlorates, so that their ash contained 

 only alkaline carbonates or carbonate of lime, with small quantities 

 of alkaline sulphates. With regard to the quantity of sulphur in 

 the peptones, I found it to be constantly the same as that in the 

 substances from which they were derived ; thus, for example, 

 in the peptone of the albumen of eggs, after deducting the 

 alkali or lime, I found in three experiments, 1*579, 1*659, and 

 l*60Og- of sulphur, the mean being 1*602^, which coincides almost 

 to the very decimal places with Mulder's determination of the 

 amount of sulphur in the albumen of the egg. This sulphur 

 appears, however, to be contained in the peptone, in precisely the 

 same form as it exists in the albumen ; at all events, when treated 

 with alkalies it yields very distinct indications of sulphur, both 

 with the salts of lead and with silver- foil. In my repeated analyses I 



