77//; iii.(K)h srcM! 641 



(2) A (Iccrcascd utilization in tlie orgjaiiism as a whole (j)aiicreatic 

 diabetes). 



(8) All iiit-reased supply to tlie kidneys resultinj^ from the libera- 

 tion into the blood of sugar previously stored or combined in other 

 orp-ans. Thus, the rapid hydrolysis of glycogen following ])un('ture 

 of the floor of the fourth ventricle and analogous nerve stiimilations, 

 and occurring in the acid, asphyxial, narcotic, thyroid, epinephrine, 

 and hypophysis glycosurias. In an analogous manner lactose may 

 enter the circulating blood from the mammary gland, and pentose 

 from unknown sources. 



(4) An increased supply to the kidneys due to decrea,sed utilization 

 in other organs. The breaking down of glycogen mentioned in (3) 

 might be so interpreted. 



(5) Decreased utilization in the kidney itself. 



(6) Increased physical penetrability of the kidney membrane to 

 glucose. Both (5) and (6) are hypothetical conditions, the latter 

 having been proposed as the basis of so called kidney diabetes, a state 

 in which glycosuria occurs with a normal or subnormal percent age 

 of sugar in the blood and in which the rate of sugar excretion is, in 

 comparison with other forms of glycosuria, little influenced by the 

 diet.-"^ 



THE BLOOD SUGAR * 



The normal blood sugar concentration is found to average 0.10 

 per cent., but, as statistics show, it may vary at least between 0.06 and 

 0.11 per cent. The literature contains numerous references to that 

 blood sugar concentration which if exceeded leads to glycosuria 

 ("threshhold" value). In accox'dance with the general principles 

 above discussed we should expect this value to vary. It has been 

 placed at 0.147 to 0.164 per cent, by Foster, between 0.17 and 0.18 

 per cent, by Hainan and Hirschman, at about 0.20 per cent, by Pavy, 

 and other writers have reported greater variations, due in part doubt- 

 less to differences in the analytical methods used. How widely the 

 threshhold blood sugar percentage may be varied by extreme variations 

 of the blood volume and other factors has not been settled. Following 

 the ingestion of free glucose the blood sugar percentage ordinarily 

 rises, and in a similar way, but more slowly, after feedings of starch. 

 Fisher and "Wishart gave 50 gm. of glucose in 150 c.c. of water by 

 stomach to dogs weighing 8 to kg. and found in the first hour blood 

 sugar percentages of 0.16 and 0.13. In succeeding hours there was 

 little variation from 0.11 per cent. In harmony Avith the previous 

 work of Gilbert and Baudoin and the more recent studies of others on 

 man. these experiments showed that the l)lood sugar percentage rises 

 during the first hour, then falls and thereafter remains iKU-mal. There 

 was no increase of the blood volume during the first hour, the hemo- 



9a Cf. Epstein, A. A. ^rosenthal. 

 41 



