A critique of Katz's 'high LET constraint on low LET survival'.

Katz's interpretation of the connexion between RBE and LET is contrasted with a version published previously by Burch. The implications of Katz's model for dose-response relations apply only at ultra-high absorbed doses in Burch's model. In the latter, the shoulder on type-C survival curves for mammalian cells is explained in terms of Haynes' repair model.

Perthes' disease: a new genetic hypothesis.

We describe the sex and age distributions of the onset of Perthes' disease in our own and six other large published series. The mathematical features of these distributions, together with the evidence for familial aggregations, agree with the theory that the disease is autoaggressive in aetiology and that two genetically-distinctive groups are at risk. We consider the frequency of affected sides - left, right, bilateral - in our own and other series: concordance for affected side(s) within sibships suggests that laterality might be genetically determined.

Hip dysplasia without dislocation in one-year-old boys.

Six boys were examined during the second year of life, each with symptoms in one hip. The affected femoral capital epiphysis was smaller or more irregular (or both) than that of the unaffected hip but was neither subluxed nor dislocated. The subsequent radiographs revealed changes similar to those in severe Perthes' disease.

Progression of tumours and non-neoplastic disorders as manifestations of a common biological phenomenon.

The thesis is presented that progression, in both neoplastic and nonneoplastic disorders, involves a common biological mechanism. This view derives from the author's unified theory of growth and age-dependent disease. Diseases that show a reproducible age-dependence, satisfying certain statistical criteria, are held to be initiated by random 'errors'--somatic gene mutations--in stem cells of the central system of growth-control.

Transscleral ocular siderosis.

Intraocular migration of iron from iron foreign bodies in an extraocular or intrascleral location was studied in rabbits. Focal changes occurred in the choroid and retina beneath the foreign bodies. Significant amounts of iron diffused through the sclera into the globes.

Perthes' disease. A study of radiological features.

A study is presented of the radiographs of 68 patients with unilateral Perthe's diseasemtwo types of Perthe's disease are identified: 'fragmenting' and 'non-fragmenting'. The two radiological types of the disease showed no significant differences in the age at diagnosis, the duration of symptoms before diagnosis and the duration of the disease. However, the radiologically-measureable results at healing, in terms of the epiphyseal, acetabular, acetabulum-head and comprehensive quotients were all very significantly worse when fragmentation had developed.