PHYSIOLOGY OF THE INVERtEBRATA. 235 



Among tlie results which have been observed by MM. 

 Eegnault, Keiset, and Jolyet are (i) that the amount of 

 oxygen contained in the carbonic anhydride exhaled is 

 smaller than that of the oxygen absorbed. (2) The respira- 

 tion of insects, when these animals are in full activity, has 

 the same energy as that of the higher Vertebrata ; while the 

 earthworms do not respire more than reptiles. (3) Respira- 

 tion in the Invertebrata diminishes (asa rule) in proportion 

 as the temperature is lowered. This is because these animals 

 are incapable of producing a sufficient internal warmth, and 

 consequently they become gradually colder until the move- 

 ment when they fall into a state of hibernal sleep, or die. 



(4) After feeding, most Invertebrates (and particularly the 

 Inseda) respire more energetically than- at other times. 



(5) All animals subjected to habitual regimen always expire 

 a little more nitrogen than is contained in the air inspired. 



(6) In inanition, the absorption of oxygen and the exhalation 

 of carbonic anhydride are greatly diminished. The fewer 

 the functions exercised by an animal, the less carbon it 

 expends. 



Dr. Moleschott* has shown that the action of light upon 

 the skin notably augments the intensity of the respiratory 

 phenomena. 



In general terms it may be stated that "behind every 

 biological activity there is an oxidation of the anatomical 

 elements. No organ escapes this law, and the nervous 

 centres are as much in subjection to it as the other organic 

 apparatus. Every thought, eveiy volition, every sensation, 

 corresponds to an oxidation of the living substance, as well 

 as every secretion, every movement, &c." 



The Polyzoa. 



In this class we have probably the representative of the 

 first stage in the evolution of the respiratory apparatus of 



* Wiener Medicinische Wochenschrift, 1885. 



