DEGENERACY TREDGOLD. 551 



The second theory of causation is that these retrogressive varia- 

 tions are not caused, but arise of themselves; in other words, that 

 they are " spontaneous " in origin. Thus, in the Report of the Royal 

 Commission on the Feeble-minded the following statement occurs: 



Both on the ground of fact and of theory there is the highest degree of prob- 

 ability that feeble-mindedness is usually spontaneous in origin ; that is, not due 

 to influences acting on the parent. 



Now, as Huxley remarked many years ago, to say that a variation 

 is spontaneous is simply to express our ignorance of its causation; 

 and it is obvious that this theory of " spontaneous variation " is 

 extremely unsatisfactory. The more we learn of the phenomena of 

 nature, the more do we find evidence of law and order ; and it would 

 be strange, to say the least, if chance and not law should control 

 what is probably the most important happening in the whole of 

 nature. 



The third view is that retrogressive germ variations have neither 

 existed ab initio nor are spontaneous in origin, but are produced by 

 the operation of natural processes and in obedience to natural laws. 

 In my opinion this is not only the most reasonable view in itself, 

 but the only one which is supported by definite evidence; and, 

 although it is not yet possible fully to explain the manner of pro- 

 duction of these germ variations, it is possible to advance certain 

 considerations which at least possess the merit of carrying us a step 

 further toward the elucidation of this problem. 



If we pass for a moment from the germ cells to consider the cells 

 of the body, we find that retrogressive changes occur under two con- 

 ditions: Firstly, in consequence of an endogenous decline of their 

 vitality; secondly, through the action of external agencies. The 

 former of these changes occurs in old age. By this is not meant old 

 age as expressed by years; some persons are old at 40, others still 

 young at 80. What is meant is that condition of senescence which 

 results from the exhaustion of the inherent vitality of the cells. 

 They are unable to function because they have come to the end of 

 their physiological banking account. Decay arising from without 

 is best exemplified by the action of such inorganic and organic 

 poisons as alcohol, lead, and phosphorus, or by toxic bodies produced 

 by certain microorganisms. These agents may bring about such a 

 deterioration of important cells and tissues that the death of the 

 individual results. The problem we have to consider is whether the 

 germ-cells may be affected by similar agencies. May they undergo 

 pathological variation in consequence of senescence? May the same 

 result be caused by adverse factors of the environment? 



To begin with the first of these questions — since the modern con- 

 ception of the continuity of the germ plasm has become popular, it is 

 not infrequently said that this plasm is "immortal." But even if 



