162 
Vines . — The Proteases of Plants (//). 
of acidity. But Dr. Vernon’s results indicate a remarkable and interesting 
convergence between the tissue-erepsins of animals and of plants in this 
respect, inasmuch as he finds the protease of the lower animals to be 
relatively more active in acid liquids than that of the higher. For instance 
he determined the ratio of the activity of glycerin-extract of cat’s kidney in 
alkaline to that in acid liquids to be 76 : i ; cat’s liver 13:1; rabbit’s kidney 
42:1; pigeon’s kidney 5:1; frog’s liver i-8 : 1 ; eel’s kidney 1-4:1; 
lobster’s liver 8:1; Anodon’s kidney 2:1. It is not inconceivable 
that, with a more extended range of observation, animals will be found 
whose erepsin, like that of plants, is more active in acid than in alkaline 
liquids. 
In this connexion I may quote an interesting passage from von 
Ftirth’s recent work on the chemical physiology of the lower animals ( 9 ). 
Comparing the proteolysing secretions of the Invertebrates with the gastric 
juice of the Vertebrates, the author states that ‘ so far the presence of free 
acid in the digestive secretions has not been demonstrated in the case of any 
Invertebrate. In certain cases, where the matter was especially investigated, 
it was clearly ascertained that the acid reaction was due to the presence of 
acid salts, and that accordingly the proteid-digestion was rather tryptic 
than peptic.’ This agrees in a remarkable manner with the view, first 
expressed by Fernbach and Hubert with regard to malt, that the natural 
acidity which is so favourable to the activity of the vegetable proteases 
is due to the presence of acid salts such as monobasic phosphate of potash 
(see my paper, No. 1 , p. 297). 
List of Papers referred to. 
1 . Vines : The Proteases of Plants ; Annals of Botany, vol. xviii, 1904, p. 289 (April). 
2 . Emmerling : Ueber die Eiweissspaltung durch Papayotin ; Ber. deutsch. chem. Ges., vol. 35, 
p. 695, 1902. 
3 . Vines: Proteolytic Enzymes in Plants (II) ; Annals of Botany, vol. xvii, 1903, p. 606 (June). 
4 . Mendel and Underhill : Observations on the Digestion of Proteids with Papain ; Trans. 
Connecticut Acad, of Arts and Sciences, xi, 190-1. 
5 . Martin : Papain Digestion; Journ. of Physiol., v, 1884, p. 213: also, Nature of Papain, and 
its Action on Vegetable Proteids ; Journ. of Physiol., vi, 1885, p. 336. 
6. Wurtz: Recherches cliniques et chimiques sur la Papaine ; Paris Medical, 1879. 
7 . Vines : Proteolytic Enzymes in Plants; Annals of Botany, vol. xvii, p. 249, 1903 (January). 
8. Vines: Tryptophane in Proteolysis; Annals of Botany, vol. xvi, p. 7, 1902 (March). 
9 . von Furth: Vergleichende chemische Physiologie der niederen Thiere; 1903, p. 254. 
