226 Notes and Memoranda. 



co-ordinates respiratory movements, and acted as their point of departure. The 

 posterior abdominal movements that assist respiration he referred to the subceso- 

 phagal ganglia, and regarded the abdominal ganglia, which are the origin of 

 respiratory nerves, as merely conductors, connected with the respiratory centre, 

 and unable to continue respiration after connection with those centres ceased. 

 M. Bandelot doubted these conclusions, and selected for his researches the larva 

 of the dragon fly, as being easier to experiment with than a Dyticus. The dragon 

 fly larva has no separate ganglia, the metathoracic being connected with the first 

 abdominal ganglion by long communications. Having removed the head of this 

 larva at noon, the respiration continued regularly to six o'clock. The next day 

 it went on feebly at nine o'clock, and only stopped about three. In a second 

 experiment he divided the body immediately behind the metathoracic ganglion ; 

 but respiration continued. From these and other experiments he concludes that 

 M. Faivre was in error, and that instead of there being only one centre of 

 respiratory action, each abdominal ganglion acts as the local centre, and combines 

 with others to produce a co-ordinated result. 



Formation oe Ice in the Sea. — M. E. Edland treats of this question in 

 JPoggendorff's Annals, and he states that in addition to the mode usual in fresh 

 water, in which the surface freezes first, and if the cold is prolonged the layer of 

 ice is thickened, it is common in the open sea for a great mass of water to be 

 reduced below the freezing point without losing its liquidity, and for it then 

 suddenly to solidify all through. 



Physical Analysis op the Human Beeath. — Mr. W. F. Barrett, Assistant 

 in the Physical Laboratory of the Royal Institution, has recently published, in 

 the Philosophical Magazine, a new and extremely delicate method of determining 

 the amount of carbonic acid in air expired from the lungs. The apparatus used 

 by Mr. Barrett in this investigation, which has been made under the general 

 direction of Professor Tyndall, is nearly the same as that employed by the 

 Professor in his researches on the absorption of heat by gases. 



Three suitable bags are filled with the human breath ; No. 1 is filled before 

 breakfast ; No. 2, after breakfast ; No. 3, after severe exertion. The contents 

 are then successively allowed to enter an exhausted brass cylinder, the ends of 

 which are stopped air-tight by plates of rock-salt. Through this cylinder the 

 radiation from a flame of carbonic oxide gas is passing. Immediately the breath, 

 which has been deprived of its moisture, fills the brass cylinder, more than half the 

 heat from the flame is cut off, or absorbed, and this entirely by the small quantity 

 of carbonic acid present in the expired air. The amount of heat intercepted by 

 the breath is, in each case, accurately measured by means of a delicate therino- 

 multiplier. The per-centage of carbonic acid contained in the different specimens 

 of breath is found by calculation and subsequent experiments, and is then com- 

 pared with a chemical analysis of each specimen made by Dr. Frankland. 



The close agreement between the methods of analysis is shown by the following 

 numbers : — 



By physical analysis. By chemical analysis. 



Bag 1 400 4-31 



Bag 2. 4-66 456 



Bag 3 533 522 



These numbers indicate the per-cent. of carbonic acid in breath, and show 

 that in these experiments the least amount of that gas was exhaled before break- 

 fast. 



Many other different samples of breath have been examined by Mr. Barrett ; 

 the results he has obtained prove the great delicacy ot the new method of analysis 

 in detecting small quantities of carbonic acid, or in discovering variations in the 

 amount of this gas in the atmosphere or in the human breath. For this purpose 

 its application in hospitals has already been suggested by eminent men. 



WSHSB* 





