The Permeability of Cells for Acids. 149 



0.5, 0.6, 0.7, 0.8, 1.0, and 1.2 c.c. n/10 acid, and the concentration noted 

 in which movement of the cilia ceased in 20 hours. To make sure that 

 the cilia had been really killed and not simply stopped by the acid, as 

 observed by Barratt 1 on Paramcecium, it was found necessary to stim- 

 ulate them mechanically. 



In table 2 the acids with nearly the same effect or property are 

 arranged in groups and in an order to correspond as nearly as possible 

 with the penetration series. An asterisk marks the acids which are 

 markedly out of place in the series. The following acids were studied : 



Benzoic, C 6 H 6 COOH = Benz. 



o-Salicylic, C 6 H 4 OH COOH = Salic. 



(o-Amino benzole, C 8 H4NH 2 COOH). 



Formic, HCOOH = For. 



Acetic, CH 3 COOH = Acet. 



Propionic, CH 3 CH 2 COOH = Prop. 



n-Butyric, CH 3 CH 2 Ch 2 COOH = Buty. 



iso-valeric, (CH 3 ) 2 CH CH 2 COOH = Val. 



(Caproic, CH 3 CH 2 CH 2 CH 2 CH 2 COOH) . 

 Monochloracetic, CH 2 C1 COOH = Monoc. 



Dichloracetic, CHC1 2 COOH = Die. 



Trichloracetic, CCls COOH = Trie. 



Hydrochloric, HC1 = Hydroc. or Cl. 



Nitric, HNO 3 = Nitr. or NO. 



Sulphuric, H 2 SO 4 = Sulph. or SO 4 . 



Phosphoric, H 3 PO 4 = Phos. or PO 4 . 



Oxalic, (COOH) 2 = Oxal. 



Malonic, CH 2 (COOH) 2 = Malon. 



(Succinic, C 2 H 4 (COOH) 2 ). 



Glycolic, CH 2 OH COOH = Glycol. 



d-and Z-Lactic, CH 3 CH OH COOH = Lac. 



/-Malic, CH 2 CHOH (COOH) 2 = Mai. 



d-Tartaric, CHOH CHOH (COOH) 2 = Tart. 



Citric, CH 2 CHOH CH 2 (COOH) 3 = Cit. 



Maleic, C 2 H, (COOH) 2 = Maleic. 



Fumaric, C 2 H 2 (COOH).. = Fum. 



The toxicity and effect of acids on many biological processes has been 

 worked out, and for the sake of brevity the results have been condensed 

 and recorded in table 3 for ready comparison with the results in table 2. 



It will be noted, from table 3, that there is no agreement between the 

 series of acids arranged in order of efficiency in affecting various tissues. 

 Take, for example, toxicity. We might expect different organisms to 

 varv in resistance to the same acid but the series of acids should be the 



/ 



same. That is, however, not the case, as a comparison of the toxicity 

 for Paramcecium, for Lupinus seedlings, and for the cilia of the giant 

 clam (table 2) will show. We can, therefore, state relations in only a 

 very general way. There is a general relation between the toxicity 

 for Lupinus and the giant clam, but it is not exact. 



Similarly, exceptions are noted when we compare the physiological 

 effect of the acids with their physical properties. One of the closest 

 parallels is between the efficiency of an acid in causing membrane 

 formation in the egg of the sea-urchin and its effect in lowering the 



it. f. Alleg. Physiol., 4, p. 441, 1904. 



