255 



ADDENDUM. 



The Acidity of Gastric Juice. — An interesting 

 self-regulating mechanism of the acidity of the gastric 

 juice has recently been described. As secreted, in 

 animals and man, the hydrochloric acid is as much 

 as 0-5 per cent, but it is neutralized, partly by food 

 and partly by the regurgitation of pancreatic and 

 intestinal juices, down to 0*2 or ot per cent, which 

 is the optimum, and in health it is maintained at 

 this standard. In hyperchlorhydria, this regulation 

 breaks down, and the acidity approximates to 0-5 

 per cent. 



The Nervous Control of Muscular Tone. — 

 A very interesting research has been published by 

 Weed, affording a different explanation from that 

 given in the text with reference to the nervous control 

 of muscular tone. This has an important bearing on 

 the explanation not only of the rigidity which is seen 

 in the body and limbs of cats after section of the 

 mesencephalon (decerebrate rigidity), but also of that 

 which accompanies hemiplegia or monoplegia in man, 

 and the occurrence of atonia in cerebellar lesions. 



According to Weed's researches on cats, the centre 

 which is responsible for the exaggeration of muscular 

 tone is the red nucleus, and it does so in response to 

 sensory stimuh reaching it from the posterior nerve 

 roots by way of the ventral cerebellar tract, cere- 

 bellum, and superior cerebellar peduncle. Section 



