Respiration in Invertebrate Animals. 1 89 



The relation of the tracheae to the blood-currents will be studied 

 under the next head. 



Peripheral extremes of the respiratory and circulatory systems in 

 Myriapoday Insecta, and Arachnida. 



In their extreme distributions these two great systems will be 

 most advantageously studied in connexion. There prevails be- 

 tween them an extensive parallelism; they are not, however, 

 everywhere in coincidence. Though much has been accomplished 

 by the ingenuity of minute anatomists during the last few years 

 to dispel the difficulties of this subject, much still remains to be 

 unravelled. Svvammerdam, Malpighi, Lyonet, and Cuvier*, did 

 really no more than discover the existence of the dorsal vessel. 

 It was at this time that Cuvier first made the felicitous obser- 

 vation, "Le fluide nourricier, ne pouvant aller chercher Fair, 

 c^est Pair qui vient le chercher pour se combiner avec lui." 

 Cuvier believed the fluids in the Insect to be stagnant, except 

 in the dorsal vessel, in which they only oscillated to and fro. 

 In the year 1827 Cams saw the movement of the blood in 

 the transparent larvae of the Ephemeridce and A^rionidaf.. 

 Carus could not trace the currents to their remote courses. 

 Wagner in 1832 J confirmed the observations of Carus. Straus 

 added his authority upon the same point. Mr. Bowerbank§ 

 has published admirable observations on the circulation of the 

 blood in the wings of Chrysqpa perla and Phlogophora meticulosa 

 in the order Lepidoptera. Mr. Bowerbank has in no instance, 

 however, followed the blood beyond the larger nervures of the 

 wings, in which he saw the current (accompanied always by a 

 trachea) turning back at certain points. He nowhere states that 

 these currents followed the tracheae to their extreme ramifications. 

 Mr. Newport corroborates these observations in his article 

 "' Insecta," in the Cyclopaedia of Anatomy and Physiology. In 

 the year 1848, M. E. Blanchard|| })ublished a celebrated essay, 

 in which he first announced the ingenious experiments w^hich led 

 him to conclude that the blood travelled everywhere in the sheaths 

 of the tracheae : — " il est demontre que le fluide nourricier 

 penetre entre les deux membi'anes qui les constituent." M. 

 Eraile Blan chard does not attempt to show how the blood 

 can describe a circuit in such a manner and in such a situa- 



* Sur la Nutrition dans leslnsectes, Mem. de la Societe d'Hist.Nat. ^e 

 Paris, 1797. 



t Nova Acta Physica, vol. xv. 1834. 



X Beobachtungen iiber den Kreislauf des Blutes, &c. bei den Insecten, 

 Isis 1832. 



§ Entomological Magazine, 1833. 



II Annales des Sciences Nat., 3^^ serie, Sur la Circulation dans les In- 

 sectes, &c. 



