1903.] On the Nucleic Acid of the Thymus Gland. 101 



of distilled water and the resulting solution was examined 

 polarimetrically. 



W = 1-109 grammes; V = 200 c.c. ; L = 200 m.m.; a = 1 43'. 

 [a] D = +154-2. 



3. 10 c.c. of the solution used in the last experiment were further 

 diluted with 10 c.c. of distilled water and the resulting solution was 

 examined. 



W = M09 grammes ; V = 400 c.c. ; L = 200 mm. ; a = +0 52'. 



The above observations indicate that solutions of the nucleic acid 

 of the thy m us are powerfully dextro-rotatory, but that the specific 

 rotation of neutral solutions does not vary appreciably with dilution, the 

 variations in the results of the three sets of observations recorded 

 above falling within the probable limits of error. Similar results had 

 already been obtained with solutions of the nucleoproteid of the 

 pancreas, although the limits of dilution in that case were not so 

 great as in the present instance. 



On the Influence of the Reaction of the Solution on the Optical Activity of 

 the Nucleic Acid of the Thymus Gland. 



The observations about to be referred to indicate a very remarkable 

 influence exerted by the reaction of the solution on the optical activity 

 of the nucleic acid under discussion. The rotation is notably 

 influenced by the acidity of the solution ; it reaches a maximum at a 

 certain degree of acidity and then decreases. On the other hand, the 

 addition of ammonia in sufficient proportion will render a solution of 

 thymus-nucleic acid optically inactive, though neutralisation of the 

 acid will restore its pristine activity. It is to be noted, however, that 

 there is no abrupt change around the neutral point, a statement which 

 is illustrated by the fact that two solutions of equal concentration 

 may be prepared which are undistinguishable in so far as their optical 

 rotation is concerned, one of which is faintly, though distinctly, acid 

 to litmus, while the other is alkaline. 



4. 25 c.c. of the original neutral solution of nucleic acid employed 

 in the first set of experiments were made decidedly acid by the addition 

 of a trace of 20 per cent, acetic acid. The change of volume was so 

 small as to be negligible. The solution was then subjected to polari- 

 metric examination with the following results : 



W= M09 grammes ; V = 100 c.c. ; L = 200 mm. ; a = + 3 30'. 

 [>] D = + 157-8. 



VOL. LXXII. I 



