210 DEPARTME'ST OF THE NAVAL SERTICE 



8 GEORGE V, A. 1918 

 EXPEEIMENTAL SWELLED CANS. 



Having isolated strains of gas-producing bacteria from swelled cans of sardines, 

 and having determined their cultural features and biochemical reactions, the next step 

 was to attempt the experimental swelling of normal cans by inocvilation of organisms 

 already isolated. Up to the present I have used three cultures for this purpose — cul- 

 tures 35, 37 and 64. These three cultures on the basis of their biological and bio- 

 chemical reactions are sufficiently differentiated (pages 199-207) to warrant indivi- 

 dual trials. A nimiber of normal cans of sardines were most courteously supplied by 

 the manager of the Chamcook factory, St. Andrews, N.B. Some of the cans were of 

 sardines packed in cottonseed oil, olive oil having been used for the remainder. The 

 cans had to be " punched," inoculated, and again sealed. In order to eliminate as far 

 as possible any error of manipulation I obtained by courtesy of the chief engineer, the 

 services of the college plumber, who undertook the soldering. To avoid trouble from 

 escaping oil, the cans were placed on end, rather than flat on the bottom. By the usual 

 method a layer of solder was first spread over a portion of the can; this I cleaned and 

 sterilized with absolute alcohol, and then with a sterile awl punched a hole 3 mm. 

 diameter. From a Ice. pipette, 2 to 3 drops of a young peptone broth culture of the 

 desired organism were quickly dropped in; a small square of sterilized tin heated in 

 the flame was at once placed over the hole, and the soldering process performed. The 

 layer of solder previously spread over the can assisted materially in making the pro- 

 cess effective. In this manner cans were inoculated with the respective cultures; the 

 control cans receiving exactly the same treatment minus the inoculation. The cans, 

 each placed in the half of a large petri dish, were incubated at a temperature of 30° 

 to 33° C. They were examined at frequent intervals, and in 4 days swelling was 

 observed in those inoculated. In 7 days the swelling has become so pronounced that 

 there appeared to be danger from explosions. The cans were examined. 



Normal Cans. — (Punched and resoldered). These appeared perfectly normal; no 

 oil in petri dish, no moisture on outside of can, no swelling, no " rattle " on shaking. 

 "VVlien opened there was no escape of gas; contents firm in texture, flesh the white of 

 the normal sardines, and comparatively dry; odour typical and mild; normal in every 

 respect. 



INOCULATED CANS. 



Can 35. — Inoculated with culture 35, oil in petri dish and on surface of can; pro- 

 nounced swelling, top and bottom of can, convex; on shaking, the typical 

 "rattle" of the original "swells"; when opened escape of gas and exuding 

 of oil. The contents were soft, moist, and disintegrated to an even greater 

 degree than in many of the original " swells." The oil was intermixed with 

 the macerated sardines, and gas bubbles were very evident throughout the 

 whole. The colour was a little darker than normal. The odour was not putre- 

 factive, but an accentuation of the typical normal swell. The conditions 

 noted were as evident on the side immediately opposite the point of inocula- 

 tion, as at the point of inoculation itself. The condition of this can and its 

 contents was in every respect identical with the conditions found when 

 examining the original typical " swells," but accentuated. 



Can 57.— Inoculated with culture 37. The description given of can 35 is here 

 strictly applicable; no variation could be noted. 



Can 6Jf. — Inoculated with culture 64. The swelling of this can was more pro- 

 nounced, otherwise the description given of can 35 is here strictly applicable 

 in every respect. 



Isolation of Organisms. — Pieces of fish were taken from the respective cans and 

 inoculated into series of liquid media; glucose peptone broth, peptone broth, and 

 nutrient broth respectively. These tubes were incubated at 37° C. for 24 hours. 



