Respiration in Inrertehrate Animals. 1 89 



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

 under the next head. 



Peripheral extremes of the re^iratery and cireulatory systems in 

 Myriapoda, 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, 

 ever\-where 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. Ssvammerdam, 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, "JjQ fluide noui'ricier, ne pouvant aller chercher I'air, 

 e'est Pair qui ^'ient 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 saiv the movement of the blood in 

 the transparent larvae of the Ephemeridce and Agrionidie-\. 

 Cams could not trace the currents to their remote courses. 

 Wagner in 1832]: confirmed the observations of Cams. Straus 

 added his authority upon the same point. Mr. Bowerbank;^ 

 has published admirable observations on the cii'culation of the 

 blood in the wings of Chrysopa 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 traehcje 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|l published a celebrated essay, 

 in which he first announced the ingenious experiments which led 

 him to conclude that the blood ti'aielled evei7where in the sheaths 

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

 penetre entre les deux membi-ancs qui les constituent." M. 

 Emile Blanchard does not attempt to show how the blood 

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



• Sot la Nutrition dans les Insectes, Mem. de la Societe d'Hist. Nat. de 

 Paris, 17^7. 



t Nova Acta Physica, vol. xv. 1834. 



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

 Isis ia'i2. 



§ Entomological Magazine, 1833. 



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

 sectes, &c. 



