BROWN-S^QUARD'S EXPERIMENTS 143 



however, the atoxyl produces less and less effect, until it 

 makes no difference. When this strain of trypanosoiues is 

 inoculated into another animal, it is insusceptible to the 

 action of atoxyl from the first. The only difference between 

 this and the results of inoculating a highly resistant animal 

 is, that the selection is for resistance to atoxyl. There is no 

 evidence that the individual trypanosomes ever acquire re- 

 sistance to atoxyl. What the temporary disappearance of 

 the parasites from the blood suggests is that all those that 

 are not naturally resistant are killed, and the production of 

 an immune race is due to the selection of inborn variations 

 towards immunity. 



Some experiments performed by Brown-Sequard provide 

 evidence of quite a different kind. 1 Sir E. Ray Lankester 

 says : " The one fact which the Lamarckians can produce in 

 their favour is the account of experiments by Brown-Sequard, 

 in which he produced epilepsy in guinea-pigs by section of 

 the large nerves or spinal cord, and in the course of which 

 he was led to believe that in a few rare instances the 

 artificially produced epilepsy was transmitted." 2 



It is impossible here to go into the details of these 

 experiments and of the results obtained. The following 

 brief account may give a general idea of what happened. 

 In a few cases the offspring of guinea-pigs thathad. been 

 rendered epileptic by operations upon the spir>^Leof4, and 



1 Brown-Sequard, "Nouvelles Recherches sur I'Epilepsi 

 Lesions de la Moelle Epinicre et des Nerfs Rachidiens," Arc 

 Path., ii., 1869; "Faits nouveaux concernaut la Physiologili 

 Arch. Physiol. Norm. Path., Hi., 1870-71 ; " Remarque sur 1'Ep 



la Section du Nerf Sciatique chez les Cobayes," Arch. Physiol. NormTfafft^ iii., 

 1870-71 ; " Quelques Faits nouveaux relatifs a 1'fipilepsie qu'on observe h la 

 Suite de diverses Le'sions du Systeme Nerveux chez les Cobayes," Arch. Physiol. 

 Norm. Path., iv., 1872; "Transmission par Hdredite de certaines Alterations 

 des Yeux chez les Cobayes," Gaz. Medicale de Paris, 1880; "Faits nouveaux 

 etablissant 1'extreme Frequence d'Etats Morbides produits accidentellen 

 des Ascendants," Comptcs Retulus Acad. ScL, Paris, vol. xciv., 1882; 

 d'une Affection due a une cause accidentelle, Faits et Argument 

 Explications et les Critiques de Weismann," Arch. Physiol., 

 "Transmission Here'ditaire de Caracteres acquis," Arch. Physiol., \i 



2 The A dvamement of Science, 1890, 



