xviii Introduction. 



as those relating to the possible modes of origination, and to the 

 available methods for the combating of disease ; neither is it 

 advisable here to occupy space in pointing out at length or in 

 detail the various lines along which the results of Comparative 

 Anatomy come to bear upon the more purely speculative questions 

 alluded to. There are, however, certain considerations of greater or 

 less general interest, either as premises or as conclusions, which a 



absence, if not of certain animal cells, still of certain animal ' cytoids ' or ' leucocytes,' 

 the vaccine poison is inoperative. For the application of such investigations to actual 

 practice see Professor Lister's Introductory Lecture delivered in the University of 

 Edinburgh, Nov. 8, 1869 ; British Medical Journal, Dec. 4, 1869. — The vexed question 

 of the method in which nerves influence nutritional processes receives considerable 

 elucidation from the facts that not only do certain Holothurioidea (Stichopus and Colo- 

 chirus) possess the power of shedding off the non -muscular elements of their in- 

 tegument as amorj)hous slimy matter upon irritation, but also that isolated fragments 

 even of their integument, in which it would appear nerve structures are contained, 

 possess the like power, and go through the process of self-dissolution more quickly or 

 more slowly in correspondence with more or less stimulation. (See Semper, Eeisen 

 im Axchipel der Philippinen, Theil. ii., Bd. i., pp. 72, 171, 172, 200.) The universally 

 acknowledged but often practically ignored influence of changes in the circum- 

 ambient medium are well illustrated by such observations as those of M. Clapar^de 

 on the growth of Annelida (see Ann. and Mag. Nat. Hist. Ser. iii., vol. xx., p. 359, 

 1867), and those of Professor Wyville Thomson on the varjnng rate of development 

 of certain Echinoderm larvae (see Phil. Trans, vol. 155, pt. ii., pp. 514, 515, 532) 

 under varying conditions of light, heat, and aeration. Dr. Charlton Bastian has 

 drawn attention (Linn. Soc. Trans, xxv., p. 84, 1865) to the quantity of large fat 

 globules often seen within the intestinal canal of free Nematodes as being ' remark- 

 able, and also interesting in a physiological point of view, as an exemplification of the 

 almost direct conversion of cellulose into fat and other products.' The facts of Com- 

 parative Anatomy and Physiology as distinct, though not dissociated, from those of 

 Comparative Pathology and Experiment, are appealed to by both sides in the ques- 

 tions ' Ueber die Fettbildung im Thierkorper,' and that of the relations of various 

 kinds of food to the various exigencies of the animal body. (See Donders, Nederl. 

 Arch, voor Genees. en Natuurkunde, Deel. i., Utrecht, 1864 ; translated, Dublin 

 Quarterly Journal of Medical Science, 1866; Lawes and Gilbert, Phil. Mag., July 

 and December, 1866 ; Voit. Zeitschrift fiir Biologic, Bd. v., Hft. i., pp. I47-155, 

 1869.) For the way in which the intimate relations of the fifth nerve to the optic may 

 be illustrated by reference to Comparative Anatomy, see Mooren, Ueber Sympa- 

 thische Gesichtstorungen, pp. 117-119, Berlin, 1869; and for numerous illustrations 

 of the fact that the organisms of the lower animals give answers in simple language 

 to what are difiicult problems in Anthropotomy, see Schroeder Van der Kolk, on the 

 Spinal Cord and Medulla Oblongata ; New Sydenham Society's Translation, passim, 

 and especially chapter vi., pp. 170-178, 1859. For other points of connection be- 

 tween Comparative Anatomy and Practical Medicine, see 'Medicine in Modern Times, 

 pp. 79-91, London, i86y. 



