Respiration in Invertebrate Animals. 191 



surface. The ultimate divisions of the trachea are always distri- 

 buted separately and do not anastomose, ending, as noticed by Mr. 

 Bowerbank, in extremely minute, filiform, blind extremities, and 

 this Mr. Newport finds to be their condition in all structures, 

 in the nervous and integumentary, in the glandular and mus- 

 cular*". M. Blanchardt has very recently proved the existence 

 in the Arachnids of a tme capillary network ? at the extremes of 

 the circulation. " This network," he remarks, " which has not 

 yet been pointed out in the Articulata, exists under the inte- 

 guments and between the various layers of the muscles, in the 

 connective tissue; it consists of distinctly circumscribed canals 

 lined with a thin epithelium. Thence the blood is received by 

 the venous canals j." Thus is presented in bibliographic but 

 faithful outline the sum of existing knowledge on the distribution 

 of the air- tubes and the blood-channels in the air-breathing 

 Articulata : who can say that it exhibits a consistent history ? 

 The physiologist rises from the scene confounded by its manifold 

 contradictions. The assertions of one observer ai-e opposed and 

 outweighed by those of another. Mr. Newport, the most recent 

 and laborious investigator, leaves the subject utterly unintel- 

 ligible ; his observations cannot be verified in nature. 



The author does not, for one moment, pretend to affirm that 

 his researches (now first published) have as yet destroyed the 

 possibility of all controversy upon every part of this subject. 

 He does, however, believe that he has finally settled one part, — 

 that which relates to the extreme distribution of the trachcse. 

 He has not definitively established, by actual demonstration, the 

 manner in which the blood is related to the extreme tracheae. On 

 this subject he will state at present only what he has clearly 

 and confidently observed. 



It should first be affirmed as an absolute principle, from which 

 there can be no departure, that a tracheal tube is an ofr-tube in 

 every part of its course. It is not, as supposed by Agassiz and 

 M. Leon Dufour§, an air-tube in its proximal moiety, and a 



* I have given in the text at length the ^iews of Mr. Newport, as 

 reported in the abstract published in the ' Annals ' ; I have indicated the 

 points in controversy by italics. They express the results of Mr. Newport's 

 last and very recent observations. It will be afterwards seen by the text, 

 that the conclusions at which I have arrived, from numerous and scrupulous 

 examinations of the very same points, differ in a remarkable degree from 

 those just communicated by Mr. Newport to the Linnsean Society. 



t Comptes Rendus, June 20, 1853, p. 1079. See also the beautiful 

 figures in his work ' Sur I'Organisation du Regne Animal.' 



X See translated abstract in the Annals and Mag. of Nat. Hist, for Sept. 

 1853. 



§ " Elles se divisent, comme dans les Insectes en general, en trachees- 

 arth-es on grand canaux aeriferes, et en trochees nutritives, qui naisent des 

 premieres, et vont epanouir leurs subtiles ramifications dans tous les 

 tissus." — Ann. des Sc. Nat. tome xv. no. 2. p. 76, 1852. 



