484 EXPERIMENT! STATION RECORD. 



stances froni the digestive juices and cell nuclei, and estimations of these bodies 

 should be included in all metabolic experiments; 



"When the 'free' purins are injested, they are rapidly oxidized and decomposed. 

 About 50-60 per cent of hypoxanthin leaves the body as urinary purin (principally 

 uric acid) within 4-6 hours, and the same percentage of uric acid appears in the 

 urine after 8-10 hours. The bound purins, however, take 1-2 days before they are 

 fully excreted. The remaining 50 per cent of the food purin is excreted as urea, or 

 as bodies intermediate between uric acid and urea. 



" By the quantitative estimations of purin bodies in food stuffs an exact forecast 

 of the exogenous urinary purin is possible, and its amount can be limited when 

 necessary by prescribing a certain diet. . . . The endogenous purin is partly derived 

 from leucocytes, but mostly from the cell changes which result in the maintenance 

 of bodily functions. . . . Trie acid is a necessary result of normal nuclein metabol- 

 ism. In disease it is symptomatic of conditions which hinder or prevent its solubil- 

 ity and excretion, and does not itself cause the lesions w r hich accompany uricacidse- 

 mia." The volume contains an extended bibliography of the subject. 



Heat values and food values, II. P. Armsby {Reprinted from Arch. Ped., %2 (1905), 

 Feb., pp. 124-130). — The author discusses body temperature, the production and 

 liberation of heat in the animal body, and related questions. 



He points out that the production of heat in the animal body is incidental to the 

 vital processes, and the heat so produced may to a considerable degree be regarded as 

 an.excretum, the body temperature within limits being due to a condition of equilib- 

 rium between heat production and heat elimination. " It is important to note, how- 

 ever, that it is not until the original chemical energy has served its physiological 

 purposes that it takes the form of heat. It is not first converted into heat, which is 

 then further converted into muscular or other work; but, on the contrary, it first gives 

 rise to the muscular or other energy required, and the latter, in performing its func- 

 tions, is degraded into heat. 



"In other words, we have no evidence that the animal body is a form of heat 

 engine. It is evident, then, that at least a part of the heat production of the animal 

 is incidental to other purposes. At the same time, of course, the heat thus produced 

 is available to maintain the body temperature, and the question at once arises 

 whether the supply thus incidentally provided is sufficient, or whether additional 

 body tissue must be metabolized simply for the sake of producing heat." 



In order to maintain approximately the same body temperature, heat must be elim- 

 inated at the same average rate at which it is produced, the three principal ways of 

 eliminating heat being by conduction, radiation, and by the vaporization of water. 

 These processes are collectively referred to as physical regulation, and act through a 

 considerable range of temperature. ' ' Necessarily, there is an upper limit beyond 

 wrhich these means of getting rid of heat become insufficient, and the fatal heat 

 stagnation begins. As we go below this limit the tendency of a falling temperature 

 to withdraw heat from the body more rapidly is met by changes the reverse of those 

 just . . . [referred to], and by their means the outflow of heat is kept practically 

 constant and there is no increase in the amount of heat produced, but rather a slight 

 decrease. 



"As we follow this experimentally, however, we reach a point, known as the crit- 

 ical temperature, at which the possibilities of this physical regulation appear to reach 

 their lower limit. The facility with which the surface of the body eliminates heat 

 can not be further reduced, and a continued reduction of the external temperature is 

 met by a marked increase in the heat production— the so-called 'chemical' regula- 

 tion. The answer to our initial question, then, is that at or above the critical tem- 

 perature the incidental heat production due to the internal work of the body suffices, 

 or more than suffices, to maintain its normal temperature, while below that point 

 additional body material must be oxidized for this special purpose. " 



