THE CAUSATION OF DISEASE. 8 1 



assuming that the variations resulting from such crossings 

 shall be always physiological ? It may be thought that it 

 is incorrect to speak of "crossings" between the members of 

 the human race, seeing that the term "crossing" refers to 

 the union of separate varieties; but, be it noted, there is no 

 strict difference between varieties of the same ..species and 

 between individuals of the same variety, seeing that no two 

 beings are exact alike, and that beings apparently very much 

 alike may in some one particular be very much unlike, so 

 that the union of two such individuals may be regarded as a 

 cross in respect of that particular. In this sense, crosses are 

 continually occurring among us. I do not assume that the 

 hypothetical variations thus resulting will consist in such 

 typical pathological states as gout or rheumatism, which have, 

 for the most part, a known etiology, but I venture to suggest 

 that certain anomalous states of the body may thus occa- 

 sionally arise, and perhaps a condition of body rendering it 

 especially prone to disease — rendering it, namely, very apt to 

 respond pathologically to certain Environments. 



2 . The Mending of normal with abnormal, — In this case the 

 result is, as we should expect, a considerable diminution of 

 the abnormality. If the normal parent be especially sound and 

 strong in that point wherein the other fails, we might expect 

 a good result, as when a man of strong and vigorous nervous 

 system, digestion, or what not, marries a woman possessing the 

 reverse. But the result may depend upon subtler conditions 

 than we can always analyse. Sometimes the union of normal 

 with abnormal may result in the complete annihilation of the 

 abnormality, on the principle of reversion by crossing already 

 alluded to. 



We now have to consider the blending of abnormal with 

 abnormal. 



3«. The abnormalities are of the same kind and affect the 

 same tissue. — Thus, the father and mother are, let us say, both 

 neurotic, rheumatic, or phthisical. In such cases there will 

 be a very strong tendency in the offspring to inherit the dis- 

 order. We have no right to assume that there will be an exag- 

 geration of the pathological state, but we should scarcely 

 expect a diminution of it. Nevertheless, if both parents 



G 



