662 



O. D. ANDERSON 



The increase in the salivary C-R is no doubt associated 

 with the generally heightened excitability and increased neuro- 

 muscular activity of the bitch when the mating period is at 

 its height. This heightened nervous irritability is probably 

 closely associated with the underlying physiological glandular 

 changes which presumably take place at the time, namely an 

 acceleration in the secretory activity of the pituitary, the 

 gonads and the thyroid. The effect upon the salivary C-R is 

 strikingly similar to that seen when a hypothyroid dog is 

 fed thyroid extract, as will be shown later. 



eoMorox REFLEX 



Ust 



Weanei 



\Whel (>s 



Text-figure 116. Chart showing the effect of lactation on the conditioned 

 motor reflex in dog 869. Note the increase in the magnitude or vigor of the 

 reflex during the nursing or lactation period and its diminution after the pups 

 were weaned. 



The conditioned motor reflex was greatly increased during 

 the lactating period. Rosenthal ('22), an associate of Pavlov, 

 found that the conditioned salivary reflex was positively af- 

 fected when a bitch was lactating. Text-figure 116 sho\vs 

 graphically the effect of lactation. The defense reflex, tested 

 during the last month of pregnancy, showed an average 

 magnitude of 37 mm; but when tested about 3 weeks after 

 whelping the puppies and at the height of the nursing period, 

 the average value had risen to 124 mm, an increase of more 

 than 200 per cent. After lactation ceased, the value dropped 

 to 27 mm. These facts are interesting in view of the general 



