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The original reports of infection by the virus of infectious bovine rhinotracheitis (IBR) emphasized the respiratory nature of the disease it produced (7). Subsequent investigations have indicated its pleomorphic character, first with the recognition of a venereal form (6 , 8 , IO), later a conjunctival type of infection (I, 9) and most recently the observations of a phase of the infection characterized by encephalitis (2, 4, 5). Serological studies and field observations have indicated that infection by this virus often does not result in any recognizable disease.

I . A total of sixty-three wether lambs, 4-6 months old, were fed on diets low in phosphorus and adequate in calcium (0*072-0.073 yo P, 0.38-0.40 % Ca) or adequate in both (0.38-0.40 yo P, 0.40 yo Ca) for 134 or 142 days. 2. Concentrations of serum inorganic P and Ca and alkaline phosphatase activity were studied during the depletion period. Bones were taken for histological analysis at the end of the 142 days. 3. After the preliminary depletion period, a metabolism study was conducted in which the effects of previous P depletion and dietary Ca:P ratio upon Ca and P absorption, as measured by isotope techniques, were studied. 4. Histological analysis of bones showed the presence of lesions characteristic of late rickets in some sheep and of severe osteoporosis in others. 5. A wide dietary Ca:P ratio had no apparent effect on P absorption when P intake was adequate. The availability of P was lowered by a diet deficient in P with a wide Ca: P ratio. 6. Previous P depletion resulted in enhanced P absorption during the first 11.5 days after an increased intake of P, but this effect was not shown during days 14-21 after the increase. 7. Ca absorption was reduced by giving a diet low in P and was increased when the intake of P was raised. 8. The response to wide dietary Ca: P ratios by ruminants and non-ruminants is reviewed, and a hypothesis, based upon a knowledge of the intestinal reaction of these species, is offered for the finding that ruminants tolerate wider dietary Ca : P ratios than non-ruminant species.Since the first detailed report on the dietary influence of the calcium to phosphorus ratio by McCollum, Simmonds, Shipley & Park (1921), the interaction between Ca and P in nutrition has been the subject of many investigations. Results with the rat, pig, fox, and chick (Bethke, Steenbock & Nelson, 1923-4;Lloyd, Crampton & Mowat, 1961 ;Harris, Bassett & Wilke, 1951 ;Mraz, 1961) suggest that the ratio of dietary Ca to P should be maintained within relatively narrow limits in order to secure maximum growth rates. In contrast, ruminant animals appear to be less sensitive to the ratio of dietary Ca to P (Theiler, duToit & Malan, 1937 In much of this work mineral balance, plasma levels of these elements, bone ash and body-weight gain, were used as measures of response. Few studies have been concerned with the influence of the dietary Ca:P ratio on the absorption of these elements. Lueker & Lofgreen (1961), using an isotope dilution technique, did not find any influence of ratios between 0.8: I and 6 : I on the absorption of P when this element was given to sheep at a level sufficient to promote adequate growth. Since a Ca:P ratio of 6: I allowed for adequate growth in ruminants when the P intake was adequate, it may be that a higher ratio in conjunction with a deficiency of P would have resulted in a depressed availability of the dietary P.In relation to gastro-intestinal absorption, the influence of previous Ca nutrition on the absorption of Ca has been studied extensively. It is well established that rats adapt ...

Twelve newborn Hereford calves from 8 herds showed extensor spasms upon stimulation and inability to rise. Neuraxial lesions consisted of widespread vacuolation interpreted as edema and seen chiefly in terminal portions of myelinated bundles and in gray substance containing heavily myelinated fibers. Genetic analysis of 2 of these herds indicated an autosomal recessive pattern of transmission tracing back to a single bull. The identity of the disease in all herds suggested that it had the same hereditary basis in all of them.