July I St, 18S7.] 



SCIENTIFIC NEWS. 



lit 



Fig. 8 represents a powerful spectroscope provided with 

 this automatic arrangement. It is provided with four prisms 

 and two half-prisms. The half-prism at the right hand is pro- 

 vided with two inclined faces, which reflect the rays back 

 again, so that the dispersion is as great as though ten prisms 

 were used. It will be noticed that the collimator, which is 



where this was done, and done so thoroughly that the oxygen 

 was found on chemical analysis perfectly pure, the same 

 discordant effects were produced. 



Dr. Richardson therefore modified the experiments ; he 

 placed the animals in a constant current of pure, freshly- 

 prepared oxygen, kept at the temperature of 60*^ Fahren- 



fig b. 



provided with an attachment for fixing it to a large telescope, 

 is on a lower level than the observing telescope. The rays 

 travel round the train of prisms in one direction, and are 

 reflected upwards, and travel back again at a higher level. 

 (^To be continued.) 



DEVITALISED OXYGEN. 



DR. B. W. RICHARDSON has recently made an obser- 

 vation which not merely places some novel and 

 interesting problems before the chemist, the physicist, and 

 the physiologist, but throws an important light on the ques- 

 tion of ventilation. 



It has long been known that animals confined in a limited 

 volume of atmospheric air soon perish; just as, under 

 similar circumstances, a burning candle goes out. TThis re- 

 sult has been hitherto ascribed simply to the progressive 

 decrease in the proportion of oxygen, and the accompanying 

 increase in that of carbonic acid, or, as it is now more 

 generally called, carbon dioxide, as well as to the ammonia, 

 watery vapour, and nondescript organic products thrown off 

 from the skin and the lungs of the animals experimented 

 upon. 



The injurious effects of these gases and vapours Dr. 

 Richardson by no means calls in question. But he points outa 

 newsource of danger in breathing air which has been already 

 inhaled, hitherto quite overlooked. It has been put on record by 

 some observers that pure oxygen acts as a stimulant, whilst 

 other experimentalists found it to produce depressing, nar- 

 cotic effects. How are such contradictory results to be ex- 

 plained and reconciled ? It was naturally suggested that 

 in the cases where depression and drowsiness were noted in 

 the animals due care had not been taken to remove the 

 carbonic acid produced by their respiration. But even 



heit. By this arrangement all impurities arising from the 

 breath of the subjects were instantly swept awaj'. 



Differences were still perceived ; some of the animals 

 were thrown into a feverish condition, whilst others re- 

 mained — for the time being at least — unaffected. But in 

 none did drowsiness or depression set in, so long as the cur- 

 rent of oxygen was kept up. Dr. Richardson was therefore 

 fortunately led to try yet another manner of experimenta- 

 tion. He collected the oxygen as it issued from the chamber, 

 and freed it from carbonic acid, watery vapour, ammonia, 

 and all perceptible impurities, so that no chemical test was 

 able to show any difference between its character and com- 

 position and those of freshly-made oxygen gas. 



But when this charge of purified oxygen was passed for 

 the second time through the chamber, a complete change 

 ensued in the phenomena produced. All the animals be- 

 came drowsy. The gas was repeatedly tested and found to 

 be pure oxygen. The current was made more rapid, but 

 the animals remained in a state of profound sleep, which 

 ultimately ended in death. 



Hence the conclusion was reached that oxj'gen which has 

 been repeatedly passed through the lungs of warm-blooded 

 animals, however thoroughly purified, no longer maintains 

 life. Whether it has acquired some property not recognis- 

 able by chemical means, or whether it has lost some pro- 

 perty which it ordinarily possesses as existing in the 

 atmosphere, it has become " devitalised." 



To prevent any misunderstanding we must here remind 

 the reader that the air inhaled by no means loses the 

 whole of its oxygen in its passage through the lungs. 

 When breathed out again such air contains a decreased pro- 

 portion of oxygen and an increased quantity of carbonic 

 acid and other impurities. But up to the present day it 

 has been taken for granted that such oxygen, if only col- 

 lected and purified, would be again fit for maintaining life. 

 It supports combustion as well as ordinary oxygen, and as 



