370 



B. ANDERSSON AND OTHERS 



(Veriiey, 1947). An osmometric analysis of thirst speaks in favour of this 

 idea (Wolf, 1950). Evidence that hypothalamic '' osmoreceptors " are 

 concerned not only with the release of antidiuretic hormone but also with 

 the development of the urge to drink has also been produced by the observa- 

 tion that injections of small amounts of hypertonic saline into the niedial 



C 



4Cl\ 



preoptic 





b/ood tugor 



PREOPTIC WAPMINQ 



ROOM 5 



j»mfc 



'"? 



mg 



SO 



Fig. 8. Profound core hypothermia induced by local warming of the preoptic 

 region in a goat exposed to a cold (5°C) environment. Polypneic panting and 

 peripheral vasodilation occurred during the sleep decline of body temperature 

 to 30°C. Note that shivering and hypothermic hyper-glycemia were completely 

 prevented during the period of preoptic warming, but occurred shortly after the 

 cessation of warming. (From Anderson, Gale, and Sundsten, 1962b.) 



hypothalamus of goats may eHcit polydipsia (Andersson, 1952 ; Andersson 

 and McCann, 1955a). But cellular dehydration is apparently not the sole 

 factor capable of eliciting the urge to drink (Holmes and Gregersen, 1950a 

 and b). Other changes in the internal environment such as a decreased 

 extracellular fluid volume and a marked hyperthermia (see below) may 

 have the same effect. 



Even more complex factors seem to determine caloric intake. Two com- 

 ponents can be separated in the regulation of food intake. There is 

 apparently one short-term regulation working to keep the daily energy 

 supply equal to the energy expenditure. In addition a long-term regulation 

 works to maintain the fat depots and thus the body weight relatively con- 

 stant, Various types of experimental evidence have been presented in. 



