The literature has become rather extensive and is nearly completely mentioned by Comby and Dieterle. Every year adds new material. The clinical picture has been completely described in detail by Kassonitz and Nathan.
The anatomical process consists in a febrile affection of all cartilagin ously preformed bones and of the cartilages. (Figs. 143 and 144.) The tubular bones are either normal in thickness or a trifle too thick, con siderably shortened and bent in their diaphyses. This is especially true of the humerus and femur. The spongiosa has wide 'fleshes and prema ture synostoses are the rule, forming a noteworthy contrast to athyreosis. The os tribasilare especially shows a typical premature synostosis which considerably adds to the shortening of the cranial base aside from the frequent hypoplasia of the cartilages. This accounts for the occurrence of saddle nose. Virchow's famous ease, which caused him to pronounce the saddle nose in athyreosis the result of pretnature synostosis of the os tribasilare of micromelia, is a true fetal claondrodystrophy, but not cretinism.
Similarly, the synostoses of the nuclei of the vertebral arches and corpuscles occur prematurely, leading to flattening and narrowing of the vertebral canal; it may, however, also be absent, and then the condi tion of the vertebral canal is occasioned by a fetal hypoplasia of the cartilages (Dieterle). Both processes, separately or combined, may lead to the well-known narrowing of the pelvis. All these synostoses and cartilaginous hypoplasias furnish proof that long before the commence ment of the normal process of ossification there was a disturbance of the first fetal cartilaginous bones.
Microscopical examination shows great abundance of cells, consider able vascularization of the cartilage and the so-called periostcal lamella: a connective-tissue tract penetrating from the periosteum into the level of the epiphyseal cartilage and reaching almost into the centre of it. Its presence can be demonstrated at the extremities as well as in the costal epiphyses. Both the periosteal and endosteal ossifications take place very energetically, forming a welcoine substitute for the insuffi cient ossification at the expense of the cartilage. This, therefore, forms another contrast to athyreosis, in which the epiphyscal cartilage remains unused as a complete disk until advanced old age, whik in inicromelia it is prematurely used up by active ossification.
Thus, in athyreosis all tissues participating in the structure of the bones suffer through arrest of development, while in chondrodystrophy there are hypoplasia and insufficient proliferation or regeneration of the cartilages alone.
Further signs of arrested fetal development in mieromelia are situs inversus, polydactylism, malformation of the lungs, heart and kidneys. Congenital goitre has also frequently been observed, but always with functional glandular tissue, and has therefore been wrongly brought into causal connection with micromelia.
2. Osteogenesis imperteeta (Vrolik).—This affection was first investigated and correctly interpreted by Vrolik in 1S-19 and has become better known under the name of osteopsathyrosis. It does not lead to micromelia in all cases, and may persist for years with numerous frac tures, without causing any abnormality in the external form of the extremities, which may even retain an unusual straightness. Enderlen pointed out that spontaneous fractures of the clavicula, tibia, femur, humerus and radius are of constant and repeated occurrence, and two observations of my own fully confirm his statement.
Blanchard's case of a girl tw-elve years old (Is76) was, in spite of forty-one fractures, as free from micromelia as F. Schultze's case fIS91) with thirty fractures occurring between the ninth month and the thir teenth year, and one of my own observations with forty fractures up to the age of twenty.
The last few years have furnished considerable material which has been collected by Dieterle up to 1905. This author described a detailed investigation of a case of severe micromelia caused by osteogenesis imperfeeta.
Macroscopic investigation shows insufficient ossification even where the diaphyses are not shortened, so that with diminutive osseous trabecula- a continuous corticalis is never formed and the periosteum often lies immediately upon the cartilage. Accordingly, the radiogram shows such considerahle osteoporosis that even the clearest pictures do not demonstrate the presence of bones for long distances. In light cases there is much osteoporosis with rather well-preserved osseous structures. Premature synostoses are absent. Occasionally the dia physes show annular kinking and ligations, causing the bone, when arrested in growth by more than half its normal length, to assume a very clumsy and distorted shape.