It has been objected to this that the guinea-pig's epilepsy may be produced by blows on the skull, and also by a destructive compression of the _nervus ischiadicus_ through the skin, and that in both cases the epilepsy may reappear in the following generation; and this, it is supposed, shows that the intrusion of microbes is excluded. If this were so beyond a doubt, and if we could exclude the possibility that there were previously various microbes within the body, which could only penetrate into the nervous substance after the cutting or destruction of the neurilemma, nothing would be gained that would in any way support the Lamarckian principle. One could only say: Certain injuries to the nervous system give rise secondarily in guinea-pigs to morbid phenomena like epilepsy, and all sorts of functional disturbances of the nervous system often appear in the next generation, including in rare cases even the phenomena of epileptic convulsions. That this is a case of the transmission of an acquired anatomical modification brought about by the injury is not only unproved, but is decidedly negatived, for the injuries themselves are never transmitted. Thus what is transmitted must be quite different from what was acquired, for no one has ever detected in the offspring the lesion of the nerve-trunk which was cut through in the parent, or any other result except the disease to which the original injury gives rise. Moreover, the inheritance of these morbid phenomena has been again brought into dispute quite recently owing to the investigations of such experts in nervous diseases as Sommer and Binswanger, and the correctness of Brown-Séquard's results, which have dragged through the literature of the subject for so long, has been emphatically denied[11]. [11] See H. E. Ziegler's report in _Zool. Centralblatt_, 1900, Nos. 12 and 13. Clearly formulated problems, like that of the inheritance of acquired characters, should not be confused by bringing into them phenomena whose causes are quite unknown. What do we know of the real causes of those central brain-irritations which give rise to the phenomena of epilepsy? It is certain enough that there are diseases which are acquired and are yet 'inherited,' but that has nothing to do with the Lamarckian principle, because it is a question of _infection_ of the germ, not of a definite variation in the constitution of the germ. We know this with certainty in regard to the so-called Pebrine, the silkworm disease which wrought such devastation in its time; the germs of the pebrine organism have been demonstrated _in the egg_ of the silk-moth; they multiply, not at once but later, in the young caterpillar, and it is the half-grown caterpillar, or even the moth, that succumbs to the disease.