*The Factors Disturbing the Development.*--As we have already shown by different examples, every step on this long road of development may become a point of fixation and every joint in this complicated structure may afford opportunity for a dissociation of the sexual impulse. It still remains for us to review the various inner and outer factors which disturb the development, and to mention the part of the mechanism affected by the disturbance emanating from them. The factors which we mention here in a series cannot, of course, all be in themselves of equal validity and we must expect to meet with difficulties in the assigning to the individual factors their due importance. *Constitution and Heredity.*--In the first place, we must mention here the congenital _variation of the sexual constitution_, upon which the greatest weight probably falls, but the existence of which, as may be easily understood, can be established only through its later manifestations and even then not always with great certainty. We understand by it a preponderance of one or another of the manifold sources of the sexual excitement, and we believe that such a difference of disposition must always come to expression in the final result, even if it should remain within normal limits. Of course, we can also imagine certain variations of the original disposition that even without further aid must necessarily lead to the formation of an abnormal sexual life. One can call these "degenerative" and consider them as an expression of hereditary deterioration. In this connection I have to report a remarkable fact. In more than half of the severe cases of hysteria, compulsion neuroses, etc., which I have treated by psychotherapy, I have succeeded in positively demonstrating that their fathers have gone through an attack of syphilis before marriage; they have either suffered from tabes or general paresis, or there was a definite history of lues. I expressly add that the children who were later neurotic showed absolutely no signs of hereditary lues, so that the abnormal sexual constitution was to be considered as the last off-shoot of the luetic heredity. As far as it is now from my thoughts to put down a descent from syphilitic parents as a regular and indispensable etiological determination of the neuropathic constitution, I nevertheless maintain that the coincidence observed by me is not accidental and not without significance.