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Tissue reaction to sutures was studied in 666 specimens obtained from patients from one day to 23 years after operation. Reaction to catgut depends on the stage of absorption and is mainly histocytic in type. Nonabsorbable sutures are encapsulated by a rim of connective tissue, while near the suture histocytes, giant cells and lymphocytes are found. This is most marked with silk and cotton, less so with Dacron, and least with nylon and wire. Tissue infiltration into the suture interstics is variable. The reactions resemble the findings in experimental animals.

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Co") VIT. BI2 EXCRETION 81 0 " Q 0 2 4 6 8 10 12 14 16 18 20 Days o f Incubatibn FIG. 3. Effect of age of culture on rate of lactate oxidation by washed cell suspensions of M . tuberculosis strain H37Ra. Curve 1 = YO optical transmission of culture. Curve 2 = optical transmission of culture concentrated 5 times. Curve 3 = Qo,.0.066 M phosphate buffer, p H 6.4; 0.022 M lactate; 6-9 mg dry wt bacterial cells/cup; Sauton's medium.age of the bacterial cells. It is manifest from the data given that rate of lactate oxidation by washed cell suspensions increases with age of the cells, reaching a maximum between the 10th and the 12th day of incubation which coincides with the middle of the logarithmic phase of growth. Upon continued incubation, rate of lactate oxidation falls rapidly reaching a minimum during the stationary phase of the bacterial growth cycle. Thus, it is evident that the tubercle bacillus responds in this respect in a similar manner to other micro-organisms( 6) and suggests that young cells de-rived from dispersed cultures might properly be more widely used in studies of the physiology of this organism. Although admittedly these data were obtained using only one strain of the tubercle bacillus and inspecting only one enzyme system, the results suggest further study along these lines. Furthermore, since it has been established that the lipid content of tubercle bacilli increases with age ( 7), which may well influence the permeability of the older intact cells, it would appear desirable to utilize the younger cells for investigative purposes. Summary. A study of lactate oxidation by washed cells of M. tuberculosis strain H37Ra revealed a marked influence of the age of the cells. Cells obtained during the logarithmic phase of growth were the most active metabolically. Previous reports indicate that radioactivity *Supported by U. S. Atomic Energy Corn. and is present in bile and feces after injection of performed at Medical D e~t . , B~M -~a v e n Nat. labeled BIZ, but observation periods were short t Research Collaborator at Brookhaven from Colfollowing study was instituted to evaluate the rate of coy excretion in bile and its role as a source of fecal radioactivity after intravenous Laboratory.and data not ( ?2 j3 ) ' The lege of Veterinary Medicine, University of Minnesota.