716 PHYSIOLOGY IN RELATION TO 



and in the orthopterous insect — ^the lungs or the tracheae, as the 

 case may be, contrast to disadvantage with those of their con- 

 geners, or adult representatives, which have come to differ from 

 them in having lost the power of reproducing lost parts. But 

 active respiration is a prerequisite for activity of function and 

 rapidity of rate of vital processes : and the absence of this is, 

 according to my argument, the cause of the presence of the re- 

 parative power. The lungs are of course all but wholly in abey- 

 ance in the tadpole, and the tracheae have no vesicular dilatations 

 developed upon them in the caterpillar forms of any insect, nor in 

 the adults of the non-volant Orthoptera. In the Phasmidae, the 

 curious ' walking-stick ' insects, we observe just the same slug- 

 gishness, combined with great tenacity of life, which we observe 

 among mammals in the Bruta. Let me add some more facts in 

 further illustration of my position. The Myriapoda, which Mr. 

 Newport has shown to possess this power of repair up to the time 

 of their final moult, are so little like the more typical insects, as to 

 have been classed with the Crustacea, by no less an authority than 

 Von Siebold. Any one, again, who will compare the simple non- 

 cellular lung of the adult Batrachian newt 8alamandra aquatica^ 

 which possesses an unlimited power of repair as an adult, but not in 

 its young stages (Bonnet, ' CEuvres Hist. Nat.' v. Pt. i. p. 294), with 

 the lung of the adult frog, will have little difficulty in under- 

 standing how their power of repair differs out of all proportion 

 more than the amount of the metamorphotic changes they severally 

 go through. The land Salamander, Salamandra terrestris, has, so 

 far as I know, escaped the hands of Spallanzani and Bonnet ; its 

 adult lung being little inferior in extent and development of spongy 

 matter to that of the adult anura, I should expect the power of 

 regeneration to be reduced to zero as in them. If the teaching of 

 Comparative Anatomy has forced me to differ from the teaching of 

 Mr. Paget, there are other facts in the same region of research 

 which, as it seems to me, put one of his other many valuable doc- 

 trines in a clearer light than even his own clear enunciation of it. 

 ' Each man's capacity,' says Mr. Paget (' Lancet,' Aug. i^ih., 1867), 

 ' for bearing a surgical operation may best be measured by the 

 power of his excretory organs in the circumstances in which the 

 operation will place him.' Now, I am inclined to ascribe the very 

 considerable, and indeed, on my views, somewhat exceptional 



