Rosanoff[64] and Orr have suggested the following hypothesis relative to the transmission of the neuropathic constitution as based on the Mendelian theory:—1. Both parents being neuropathic, all children will be neuropathic; 2. One parent being normal but with the neuropathic taint from one grandparent, and the other parent being neuropathic, half the children will be normal but capable of transmitting the neuropathic constitution to their progeny, and half will themselves be neuropathic; 3. One parent being normal and of pure normal ancestry, and the other parent being neuropathic, all the children will be normal but capable of transmitting the neuropathic makeup to their progeny; 4. Both parents being normal, but each with the neuropathic taint from one grandparent, one-fourth of the children will be normal and not capable of transmitting the neuropathic makeup to their progeny, one-half will be normal but capable of transmitting the neuropathic makeup, and the remaining one-fourth will be neuropathic; 5. Both parents being normal, one of pure normal ancestry and the other with the neuropathic taint from one grandparent, all the children will be normal; half of them will be capable and half not capable of transmitting the neuropathic makeup to their progeny; 6. Both parents being normal and of pure normal ancestry, all the children will be normal and not capable of transmitting the neuropathic makeup to their progeny. Just how much importance is to be attached to these theories is a difficult matter to determine. A study of a considerable number of families by Rosanoff[65] would appear to be very suggestive, although his conclusions must be looked upon as fairly conservative:—"On the whole, taking into consideration the limited amount of material as well as the various sources of possible error, the correspondence between the actual findings and theoretical expectation, as shown in the table, must be regarded as strikingly close." On the other hand, as White[66] says, "In dealing with the subject of heredity, however, it must not be forgotten that our ideas are of necessity largely founded upon hypotheses, as biological science has not yet unfolded a sufficient number of facts to make it possible to tell just how much, in any individual case, must be attributed to the inherent qualities of the "germ plasm" and just how much to the influences of environment. The view which is pretty generally admitted among biologists at present is that there is little warrant for the belief in the Lamarckian hypothesis of the inheritance of acquired characters."