On the other hand, we have here to- notice, in a general way, the laws which nature observes in the production of malformations, so far as a general working out of this subject has revealed them to us.

1. The worst malformation is never so anomalous as not to bear the general characters of animal life, and the external semblance of the particular class of animals to which it belongs. Even an individual organ never departs from its normal character so completely that, amid even the greatest disfigurement, this character should not be cognizable.

2. Deviations from the normal are, then, confined within certain limits, and this applies in an especial manner to anomalies of position. Although that which should lie on the right may appear on the left, and the converse - the abdominal organs occupy the thorax, and the thoracic the abdomen - the brain has never yet been found in the chest or abdomen, nor the kidneys within the skull. The natural history of development reveals the cause, - different organs and systems being developed out of different layers of the germ; those pertaining to the same layer may indeed err as to their locality, but in no instance will an organ pertaining to the animal, become evolved out of the vegetative layer of the germ, nor the converse. Fleischmann calls this the law of localities (lex topicorum).

3. To this we may add, that certain conjunctions between organs, for example, the aorta and the intestinal canal forming a single tube in common, never occur; but that, as a rule, homogeneous or kindred parts alone unite, a law termed by Fleisehmann the law of individuality (lex proprietatis).

4. The excessive development of one part determines the imperfect, retarded development of another, and the converse. Meckel having laid it down as the next thing to a law, that a preponderance of one organ is associated with the retarded growth of another, Geoffroy St. Hilaire has invested this law - as the law of compensation (loi de balancement) - with the most ample significance and extension. The said law has in reality sundry facts for its foundation; it is alleged, in particular, that individuals having on one hand or one foot a supernumerary finger or toe, are often found wanting in a finger or toe on the other foot or hand. A foetus described by Neumann had on the left foot only the great toe, but, on the right, eight toes, the eighth being cleft. Segala's foetus had no thumb to the left hand - to the right, two; it had on one side eleven ribs only, but thirteen on the other. In cases where more or fewer important parts are wanting or imperfectly developed, we often find supernumerary fingers and toes; for example, in anencephalia, cyclopia, spina bifida, hare-lip, cleft abdominal parietes, etc. In the siren-malformation there is, according to Meckel, always an excessive number of vertebrae and of ribs. In acephali, deficient in heart and liver, the kidneys are asserted by Elben to be preternaturally developed. On the other hand, in the double formation of individual parts, others are frequently imperfect: thus, bitruncate malformations are frequently acephali, whilst the bicephalous have often spina bifida; and in either case sundry other organs besides have suffered an arrest of development, being deficient in abdominal parietes, the intestinal canal being imperfect, the urethra imperforate, or cloacal malformation present. Meckel has even made this law apply to different children of the same parents: one girl had on each hand a supernumerary finger, her sister had two fingers wanting to one hand.

Meckel, rightly, we think, rejects the assumption of a law of compensation, where compensation is so far from general, and admits only that malformations are often influenced by a law common to organized bodies.

5. Not every organ or part is in an equal measure obnoxious to malformation. According to Meckel it is far more rare in organs supplied by cerebro-spinal nerves (muscles, larynx, lungs), than in those supplied by the sympathetic (the digestive, urinary, generative). The vascular system is, however, most liable of all.

6. Certain malformations affect certain organs. Thus, it is an admitted fact that formations resulting from the vegetative and the vascular layer of the germ seldom multiply, compared with those which result from the animal layer. Instances of multiplied heart, lungs, intestinal canal, uropoietic and generative organs, are far more rare than of multiplied head, organs of sense, extremities, etc.

7. Whilst certain malformations are about equally frequent in both halves of the body, certain others affect by preference the one or the other side of the upper or the nether half of the body. Where the vertebral artery originates immediately from the aorta, "this," observes Meckel, " happens invariably on the left side." Cleft lip and cleft palate are commonly found on the right side. Malformations from superfluity are much more frequent in the upper than in the nether half of the body. Thus, bicephalous monsters with a single trunk are more frequent than monocephalous with double trunk; supernumerary fingers than supernumerary toes. In like manner, anomalous bloodvessels are more common in the superior extremities than in the inferior.

8. Female malformations are, by all accounts, much more frequent than male. A reason for this cannot at present be assigned.

Of the hereditary nature of malformations, and their repetition in children of the same parents, Meckel has collected numerous examples. The entail is transmitted equally through the male and through the female line. Meckel adduces an instance of a man with six fingers to each hand and six toes to each foot transmitting the same malformation to his eldest son, whose three sons again were born with precisely the same redundant organization.

Various and manifold as are the forms of monstrosity, some of them recur with such uniformity of type, as to constitute a regular series. This applies to every organ, each being especially liable to some particular kind of malformation. This circumstance is of great importance in summing up the causes of malformations. It indicates that, in the majority, not an extrinsic, accidental cause prevails, but an intrinsic one, inherent in the laws of germination and development.