GENETIC TYPE AND THE ENDOCRINES 663 



behavior of dogs during pregnancy and the altered behavior 

 during lactation. The pregnant bitch gives no behavioral 

 sign to indicate an awareness of pregnancy until a day or so 

 before whelping, when she will, if permitted, seek an appropri- 

 ate nesting place. As soon as she whelps, her behavior changes. 

 If she is normally docile and friendly, she may become hyper- 

 irritable and aggressive. This was true of the animal under 

 study. A previously gentle animal, she now continually 

 snarled and attempted to attack the experimenter or anyone 

 approaching her and the puppies. She was also very restless. 

 After the puppies were weaned she returned again to her 

 docile behavior. 



These changes in behavior are accounted for by the marked 

 changes in the internal secretions of the lactating animal. 

 The increase in thyroid activity may be largely responsible 

 for the increase in nervous excitability, and the disturbance 

 in body calcium may be linked with the excitement. There 

 is abundant evidence for such views. One has only to recall 

 the marked disturbance of central nervous function and neuro- 

 muscular coordination observed during parathyroidectomy, 

 associated with changed balance in blood calcium. It is also 

 well known that the nervous disturbance of lactating cows 

 affected with so-called "milk fever" (convulsive seizures, 

 lethargy, coma) is accompanied by a hypocalcaemia of the 

 level usually found in parathyroid tetany. 



THE INFLUENCE OF THE THYROID AND THE PARA- 

 THYROIDS UPON THE REFLEX BEHAVIOR 



The influence of the thyroid upon conditioned reflexes has 

 been the subject of previous investigations. The effects of 

 thyroid feeding upon the salivary C-R in the dog have been 

 studied by several workers. Zawadowsky, Sacharow and 

 Slotow ( '29) reported that the C-R showed an initial de- 

 pression and a subsequent stimulation. Crisler, Booher, Van 

 Liere and Hall ('33) observed the opposite, namely, that 

 the C-R showed an initial stimulation followed by depression. 

 Kleitman and Titelbaum ('36), working with the defensive 



