The distribution and topography of the mesonephric and metanephric arteries is in general accordance with the literature. The process of glomerular degeneration in the mesonephros seems similar to glomerular senescence in man but is different from that of the aged rat glomeruli. The round angiogenic buds observed in the metanephros resemble tumoral angiogenic buds in some aspects. However, both angiogenesis and the degenerative phenomena are part of the normal developmental process. Consequently, the involved mechanisms are probably under sole genetic control. The system studied here offers therefore the possibility to study vascular growth and degeneration on the same model in physiological conditions without application of vasoactive or pathological agents.

In a retrospective study, 47 fractures of the femoral neck and 17 capital epiphyseal separations were recorded in a total of 62 animals over a 12‐year period. It was found that cats sustain femoral neck fractures more often than capital epiphyseal separations. Until cats are six months old the vast majority of lesions in the proximal femur are fractures of the neck. Between the ages of six and 12 months both lesions are equally represented. After 12 months of age no capital epiphyseal separations occur and the incidence of femoral neck fractures diminishes appreciably. If left untreated, an acceptable clinical result can be obtained in both femoral neck fractures and capital epiphyseal separations, although the best functional result is achieved in femoral neck fractures. In the present study, spontaneous healing was seen only in femoral neck fractures in cats younger than three months. All cats with capital epiphyseal separations developed hypertrophic pseudoarthrosis.

In a retrospective study, 79 untreated luxations of the coxofemoral joint in cats were recorded over a 12‐year period. Twenty‐nine of these cases were available for follow‐up, of which 13 were re‐examined clinically and radiologically. It was found that the maximum incidence of the injury occurred from one to three years of age. Follow‐up radiographs showed that the cats had developed nearthroses of various degrees located dorsally on the ilium. The degree of nearthrosis formation was not consistently correlated with the length of the observation time. Radiological signs of decreased bone density of the proximal femur may be caused by reduced weightbearing related to changes in biomechanical function and altered blood supply in the luxated limb. Almost two‐thirds of the re‐examined animals presented some kind of locomotor dysfunction on clinical examination. Limb function improved with time. The best clinical results appeared to be in cats that were immature at the time of injury and developed nearthrosis similar to a normal coxofemoral joint. All the cats available to this study showed acceptable functional results and had a normal level of activity according to the owners.

SummaryA technique to obtain microvascular corrosion casts of the G2.0 rat fetus and the normal pattern of the main arteries of the G20 rat fetus are described. The casts were studied by means of scanning electron microscopy (SEMI.The arterial pattern is similar to that described in the adult; however, several variations have been found. It is concluded that the use of vascular corrosion casts studied by SEM may be particularly helpful to observe the extremely small arteries of rat fetuses. Moreover, we suggest that this technique may be useful in practical teratological studies..