Lastly, the qualities of the mind are, perhaps as much as the bodily configuration and powers, subject to influence from the hereditary in fluence of parents upon their offspring. The powers of observation, memory, judgment, imagination, the fancy, and all that belongs to what is usually called genius, the emotions, passions, desires, and appetites, as inborn mental qualities of the offspring, are all liable, to be influenced in the act of generation by the parents" The hereditary predisposition of man and ani mals to particular diseases also illustrates in a striking manner the general law now under con sideration, and from its importance in reference to life assurance has attracted considerable at tention.
Almost all the forms of mental derangement are more or less directly hereditary, one of the parents or some near relation being affected. Of bodily diseases, pulmonary complaints, diseases of the heart, scrofula, rickets, worms, gout, rheumatism, hemorrhoids, hypochotulri asis, scirrhus, apoplexy, cataract, amaurosis, hernia, urinary calculi, may be mentioned as examples of diseases more or less directly transmitted as predispositions from parent to offspring. The goitral and cretinous affections combined with deficient intellect are striking examples of the effect of hereditary influence combined with that of the situation in which the cretins live. The union of goitrous per sons in particular districts leads to the pro duction of cretins, while the union of a cretin with a healthy person tends to the improve ment of the offspring, or its gradual return to the healthy state.
The predisposition to disease may be trans mitted to the offspring from either parent, end from the one as often as from the other, but much more certainly when both the parents have been affected with the disease.
We may also mention, in connection with this subject, the transmission to the offspring of various marks and deformities in the struc ture of the parents or their relations. The cretinism already mentioned is one of these, and there are numerous other cerebral de formities which are so transmitted, as congeni tal malformations, such as the acephalous and anencephalous states, spina bifida, cyclopia, &c. which run remarkably in particular families. In many instances the hereditary cause of these deformities has been distinctly traced to one or other of the parents. Nevus, moles, growths of hair in unusual places, hare-lip, deficient or supernumerary toes or fingers, have all been traced to hereditary influence, and probably as often to the one parent or his family as to the other. Malformations of the
heart, congenital hernia, and indeed most other malformations, are capable of being traced to a similar origin.
Were further illustration of this general law requisite, it would be found in the resem blance of mules or hybrids produced by the union of two distinct races, varieties, or species of animals, which productions also afford an excellent opportunity of observing and comparing the amount of hereditary in fluence exerted by one or other of the parents. The hybrid usually combines to a certain ex tent the qualities of its father and mother, as in the familiar example of the common mule between the male ass and the mare, or in the product of the tiger and the lion, the dog and wolf, the pheasant and black grouse, the gold and common pheasant, and others. In some mules the qualities of the father predominate, in others those of the mother ; but so far as we are aware, the isolated facts regarding this point have not yet been brought under any general law.
It has been asserted that acquired qualities, whether mental or bodily, of the parents are capable of being transmitted to their offspring. Thus the superiority of a civilized over a bar barous nation is said to depend, not solely on the influence of an advanced state of educa tion upon each new corner, but also on the greater natural powers of the children, derived from their parents at the moment of their production, or, in other words, the greater capability of the children to receive the higher mental acquirements and more refined ideas belonging to the civilized condition of society.
Farther, it is asserted that dogs and cats which have accidentally lost their tails have brought forth young ones with a similar de formity. Blumenbach affirms that a man who had lost his little finger had children with the same defect. A wound of the iris and a defor mity of the finger occasioned by whitlow are said to have been transmitted. The well-trained pointer of this country produces a puppy much more capable of being trained than the dogs of the original breed. The retriever spaniel and the shepherd's colly are said to do the same. Well-broken horses produce docile foals, and lastly, the young of foxes living in hunting countries are naturally much more circumspect than those living in countries where they are not exposed to the danger of pursuit.