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The reversal of the carbon monoxide inhibition by bands of monochromatic light was determined for the oxidative demethylation of codeine and monomethyl-4-aminopyrine and the hydroxylation of acetanilide by rat liver microsomes and for the hydroxylation of 17-hydroxyprogesterone at carbon-21 by bovine adrenocortical microsomes. Maximum reversal occurred at 450 millimicrons, the light absorption maximum of the CO compound of the CO-binding pigment of microsomes. The agreement between photochemical action spectrum and spectrophotometric difference spectrum supports the conclusion that the CO-binding pigment is the terminal oxidase of mixed function oxidase systems of mammals.

The phenomenon of "growing old" is the summation of the degenerative changes which occur in all tissues. Some tissues undergo demonstrable degeneration at earlier ages than others. The degenerative changes are grossly apparent in some tissues and afford a definite index of the structural age of the host.The degenerative changes in articular cartilage appear at a relatively early chronological and structural age and in a manner which is easily demonstrable. Evidences of degenerative arthritis have been found in the skeletal remains of prehistoric animals and man. Domesticated animals and wild animals in captivity (Fox, '39) exhibit varying degrees of damage in articular cartil2g.e and adjacent joint structures. The genesis of such alterations is little understood although it is generally agreed that their frequency increases with advancing age. The present paper deals with the effect of aging on the metabolism of bovine articular cartilage. Previous investigations of cartilage metabolism were carried out with cartilage derived from varying sites, species, and ages of animals (Hoffmann e t al., '28; Dickens and Weil-Malherbe, '36 ; Bywaters, '37 ; Hills, '40). The detection of metabolic alterations incident t o aging, however, requires a material homogenous as to species and type of cartilage.Bovine material fulfills this requirement. One type of joint yields sufficient material f o r measuring several metabolic functions in an individual animal in spite of the sluggishness of cartilage metabolism. Cattle ranging from 6 weeks to 11 yea]-s of age are available in the abattoirs. The increasing frequency of degenerative arthritis in the aging animals makes this species appropriate for studying the interrelationship of aging, degeneration and metabolic activity. 1Aided in part by a grant from the Bryii Mawr Fund for the Investigation of Chronic f Synonyms employed by various authors : hypertrophic arthritis, osteoarthritis, senescent Arthritis.arthritis, degenerative joint disease. 221

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