RESPIRATION 



687 



as to the origin of the central nervous system disturbances observed. One 

 explanation is that only specific regions of the central nervous system are 

 permeable to arsenite and one would not detect this in measuring the respir- 



ation of the cerebral cortex. Another explanation is that some effect other 

 than depression of respiratory systems is involved. Indeed, one wonders 

 if direct central actions are exerted in these acute experiments, since the 

 behavior of the animals could be explained in other ways. The difference 

 is response of the liver when the arsenite was given by the two routes is 

 not easy to interpret, unless the arsenite can more readily act on the liver 

 when administered into the abdominal cavity. 



Huston and Martin (1955) injected 25 mg/kg sodium arsenite intraperi- 

 toneally and sacrificed the rats at 30-45 min. The tissues were sliced and 

 either placed on mats suspended in a gas phase or put into media. Both 

 Krebs-Ringer-phosphate and the Krebs medium III were used; the latter 

 is a phosphate-bicarbonate medium with pyruvate, fumarate, and gluta- 

 mate in addition to glucose (see accompanying tabulation). Changes of 



less than 10% were considered to be without significance. The higher inhibi- 

 tions when the tissues were suspended on mats were attributed to the fact 

 that the arsenite and thioarsenites are unable to diffuse out of the slices. 

 Again it is evident that the respiration of the brain is unaffected; even sev- 

 eral successive doses of arsenite, making the animals hypothermic and 

 toxic, produced no inhibition in the brain. The different results in the two 



