The second class has two subdivisions.

I. Double malformations from coalition. II. Double malformations from implantation.

The first subdivision breaks up into four orders.

1. Coalition without separation at either end of the body.

2. Coalition with separation at the upper end.

3. Coalition with separation at the lower end.

4. Coalition with separation at both ends.

In this classification, as in those of Breschet, double formations are made distinct from malformations through excess of parts.

The most recent classification is that of Otto. It approximates to those of Buffon, Blumenbach, and Meckel. It arrays malformations in three classes.

First Class

Monstra deficientia, furnishing three orders.

1. M. perocephala, deficient in some one portion of the head, of which there are seven species.

2. M. perocorma, malformations with deficient vertebral column.

3. M. peromela, deficient development of the extremities.

Second Class

Monstra abundantia. These are divided into two orders.

1. M. ex duobus coalita.

2. M. luxuriantia.

Third Class

Monstra sensu strictiori deformia. It resolves itself into four orders.

1. M. fissione deformia.

2. M. coalitu singularum partium deformia.

3. M. atresia deformia.

4. M. morbis manifeste deformia.

To this system there is much to object: for example, that perverse site, that anomalies with respect to bloodvessels, and certain hermaphrodite formations, have no place in it; that fissures and atresise are not admitted as monstra deficientia; that monstra abundantia are ascribed to coalition, etc.

Lastly, Bischoff begins by showing that for a classification of malformations the anatomical character alone can be made available, and that the physiological principle is here altogether inapplicable. Having then pointed out the proper method of determining the anatomical character - the diagnosis - of a malformation, he proceeds to build up the following system, which, generally approximating to those of Buffon and Blumen-bach, frequently differs from both in detail, whilst by its rigid adherence to anatomical principles, it seems to take the only admissible ground.

First Class

Malformations deficient in some essential attribute of their kind.

Second Class

Malformations possessing more than pertains to the standard of their kind.

Third Class

Malformations, the organization of which does not conform with the standard of their kind, but without either the deficiency or the superfluity just referred to.

First Class

The causes to which the malformations, here under consideration, are due, may be very various. In many instances we are justified in regarding them as products of imperfect conception, whether the fault lie in imperfect formation of the ovum or in anomalous quality of the semen. At this day, however, so much in this assumption is still hypothetical that we are compelled to deal with it cautiously, addressing ourselves, where it is possible, to other causes, more especially to interrupted evolution of an organ out of its germ, or to its development being impeded through external influences, such as impressions wrought upon the mother; destruction of the organ, in the progress of its development, through disease, particularly through dropsical accumulation; finally, destruction of an organ through mechanical influence - for example, the amputation of a limb by means of the umbilical cord or a pseudomembranous formation within the ovum, etc.

This class comprises the following orders:

1. Deficiencies in a stricter sense.

2. Malformation from diminutiveness of parts.

3. Malformation from coalition (symphysis).

4. Atresiae.

5. Cleft-formation.

Second Class

Here we meet with a regular progression, from the supernumerary bone or finger up to the development of two perfect individuals, united only at one part. The series of this progression is so graduated and so complete, that Bischoff regarded it as impracticable, even on anatomical grounds, to make any break in the respective formations, although Breschet and Gurlt have done this by distinguishing formations possessing single supernumerary parts with a single head and trunk, from those in which these latter are twofold, and which they denominate twin-malformations. This distinction is, however, based upon a physiological principle in itself objectionable. It is only to the former species of malformation that we assign excess of plastic vigor as the source of the supernumerary parts; whilst true twin-formations are referred to the fusion or coalition of double primitive germs, implying deficiency of plastic vigor, inasmuch as each germ individually must be imperfectly developed.

This class comprises the following orders:

1. Malformations from superfluity of single parts, with a single head and trunk.

2. Twin malformations with double head and trunk.

3. Double malformations from implantation.

4. Triple malformations.

Third Class

Its defect is that its characteristics are principally of a negative kind.

The objects comprised in this class being very numerous, their probable sources are in a corresponding degree various. For several formations no other cause can be assigned than an anomaly of plastic activity originating in some primitive configuration of the germ; in a few other instances disease may be assumed as the cause; the majority, however, will be explicable on the ground of arrest of development.

This class contains the following orders:

1. Change in the position of organs.

2. Deviations in the form of organs.

3. Deviations in the origin and the disposition of the arteries and veins.

4. Hermaphrodites.

As, according to our plan, all malformations will be considered under heads corresponding with the classes and orders of the above system, and as we shall also follow Bischoff in our physiological notice of the species, an occasional reference to this system will, for the present, obviate the necessity for a further enumeration of the species belonging to each order.