The Puering, Bating & Drenching of Skins

by Joseph Turney Wood

B. erodiens does not secrete any tryptic enzymes, hence its action on the skin is to be attributed either to an intracellular enzyme, or to its chemical products, which, being secreted in situ, have a more favourable and powerful action than if merely added to the bating liquid. It was for this reason that I proposed to use a mixed culture of bacteria, especially bacteria from the sweating process (see p. [105]), which secrete a mild form of proteolytic ferment, capable of dissolving the more easily soluble portion of the skin fibres (or certain constituents), but not capable of attacking the hyaline layer.

No. of the Bacterium	Where Found	Shape and Arrangement	Motility	Growth on Gelatin	Growth on Agar-agar
1	Dog dung	Small rods of the size of the Bac. prodigiosus.	Lively	In the gelatin stab-culture the bacteria show a good growth in the depth. At the surface it forms a small white button. The gelatin is not liquefied. The colonies which have reached the surface of the gelatin-plate spread in the shape of a leaf, with a mother-of-pearl-like gloss.	A white surface layer is formed on in­clined stif­fened agar-agar.
2	Do.	Small rods of the size of the hay bacillus.	Do.	Stab-culture: The germs develop along the entire track. Small arms extend sideways into the gelatin. A white layer is formed on the surface. The gelatin is slowly liquefied.	A yellowish-white layer is formed along the in­ocu­lat­ing stab.
				Gelatin-plate: When they reach the surface, the colonies spread out in the shape of a leaf and then are slightly fluorescent.
3	Do.	Very small rods rounded at the ends.	Do.	Stab-culture: Very good growth in depth. Very many arms extend laterally from the track of the stab into the gelatin. Small knots are formed at the ends of the arms. A thin white coating is formed on the surface. Gelatin is not liquefied.	A white deposit is formed on in­clined agar-agar.
				Gelatin-plates: The colonies located deeper down appear as pale-yellow small round disks, which gradually work up toward the surface and there form circular disks which show larger dots in the middle.
4	Do.	Small rods as large as hay bacilli.	Slow movement	The gelatin stab-culture resembles that of the hay bacillus, while the growth in the gelatin-plate more resembles that of the anthrax bacillus. Threads extend from the liquid colonies which have been let in, which threads are at first braided and twisted, and later on extend straight into the gelatin.	Heavy white de­posit on the entire surface.
7	Do.	Small rods simi­lar to the hay bacillus.	Lazy	Stab-culture: Strongly liquefying. A white skin forms on the surface. Along the liquefied prick are radiations into the solid gelatin.	White unevenly thin layers with spurs.
				Gelatin-plate: Quickly liquefying colonies which form a white skin at the top.
11	Do.	Medium-sized small rods.	Motile	Stab-culture: A white coating is formed on the surface. The gelatin is not liquefied. The bacteria grow well in the depth.	A white deposit along the punc­ture.
				The colonies which come to the surface spread out leaf-like with a mother-of-pearl-like gloss.
12	Dog dung	Medium-sized small rods.	Lively	Stab-culture: Grows evenly along along the track. Gelatin is not liquefied. A thin glossy deposit on the surface.	Heavy white de­posit; glossy.
				Gelatin-plates: The lower-lying colonies appear as pale-yellow circular small disks. Braids are noticed in some colonies similar to the superficial colonies of Proteus. Strong decaying smell.
13	Do.	Do.	Motile	Stab-culture: A thin coating forms on the surface. The bacteria grow downward bristle-like. Small buttons are formed at the ends of the bristles.	White deposit along the punc­ture.
				Gelatin-plates: Leaf-like, mother-of-pearl glossy, spreading.
38	Pigeon and poultry dung.	Small rods	Lively	Stab-culture: Bag-shaped liquefying of the gelatin, the same being coloured yellow.	Yellow spreading over the sur­face of the cul­ture me­dium.
				Gelatin-plates: The deep-seated colonies are granular, yellow. Those that have forced their way to the surface form white glistening small buttons.
40	Do.	Do.	Do.	Stab-culture: A white heavy deposit is formed on the surface of the culture medium; grows very well along the track.	White irregular deposit.
				Gelatin-plates: Leaf-like deposits with line system.
42	Do.	Do.	Do.	Stab-culture: A white heavy Spreading. Very good growth along the prick.	Do.
				Gelatin-plates: Leaf-shaped deposits with line system.
43	Do.	Large, grouped, grape-like.	Not motile	Stab-culture: The gelatin is slowly liquefied. Only slight growth in the depth. The culture medium is coloured chamois colour.	White puncture in yellow.
				Gelatin-plates: Yellow disks.
44	Pigeon and poultry dung.	Small rods, quite different in size.	Lively	Stab-culture: A heavy white spreading on the surface. Very good growth along the prick.	White irregular deposit.
				Gelatin-plates Leaf-shaped deposits with the line system.
45	Do.	Small rods	Do.	Stab-culture: A heavy white spreading on the surface. Slight growth only in depth.	Very thin deposit.
				Gelatin-plates: Leaf-shaped deposit with clear line system. The entire colonies appear much thinner than those of the preceding numbers.

(continuation of table to right)

No. of the Bacterium	Growth on Potatoes	Growth in Milk	Best Growth at—	Development of Gas	Special Remarks
1	The bacterium shows only a weak growth on potatoes. It forms a yellow layer.	Milk is not changed	37° C	Only slight	Without doubt a variety of bac­ter­ium Coli commune.
2	Dirty yellowish layer.	Milk remains unchanged.	Room temp.	Does not occur	—
3	Yellowish de­posit at the place of in­ocu­la­tion.	Milk is caused to curdle only after it has been in the incubator for four days.	37° C	Very pronounced. From fifty cubic centimeters of broth 6·5 cubic centimeters gas were produced in fifteen hours, of which 3·5 per cent. was oxygen, 10·7 per cent. carbonic-acid gas, and 85·8 per cent. nitrogen.	Culture-medium to which blue litmus is added turns red.
4	White, dry, spread­ing.	Milk is changed. Serum is sep­ar­ated out.	Do.	Does not occur	—
7	White, dry.	Strong serum formation.	Do.	Do.	—
11	Yellowish glossy deposit.	Milk curdles	Do.	Weak	Strongly resembles the bac­ter­ium Coli commune and differs therefrom only in that the milk curdles quicker.
12	Yellowish glossy covering.	Milk becomes pappy.	37°C	Considerable. Five cubic centimeters of gas will be developed from fifty cubic centimeters of common broth in an incubator during the first fifteen hours and six cubic centimeters during the first forty-eight hours, con­sist­ing of 12·12 per cent. carbonic acid, 3 per cent. oxygen, and 84·9 per cent. hydrogen. The gas obtained from a culture-medium containing grape-sugar con­tains about 40 per cent. carbonic acid.	If 0·25 cubic centimeters of broth-culture are injected under the epigastrium, the animal is taken violently ill. After four hours violent diarrhea occurs. Soon the mouse can hardly move; looks bristly. On the third day the animal dies. On opening the body a strong putrid smell is noticed. Some of the injected bacteria are found in the blood. The intestines are coloured green and black. The other organs are pale.
13	Glistening, yellowish.	Strong curdling.	Do.	Weak	In old stab-cultures a brown discoloration of the culture-bed is noticed along the length of the stab. Differs in the gelatin stab-culture from the common bacterium Coli commune likewise in the curd­ling of the milk.
38	Yellow glistening deposits.	Milk is not changed.	Do.	Not noticed	—
40	White, glistening. Only very slight growth.	Do.	Do.	Weak. Is only noticed in culture-bed con­tain­ing grape-sugar.	—
42	Sulphur yellow, glistening.	No change of the milk.	Do.	Strong only in media con­tain­ing grape-sugar.	—
43	No growth	Do.	Do.	None	—
44	Weak de­vel­op­ment. The cul­ture is sulphur yellow.	Curdling	Do.	Very weak. Only in media con­tain­ing grape-sugar.	—
45	Weak yellowish deposit.	Milk is not changed.	Do.	Not noticed	—

The practical difficulty is to keep such cultures uniform during propagation, and so far this has prevented their introduction in practice. Similar difficulties have influenced the use of pure cultures of yeast in the brewing of English beers, although the use of a single species of yeast is common in the low fermentation breweries on the Continent.

I found in studying the bacteria of dog dung, that the species existing in the fresh dung, which developed in ordinary plate cultures, appeared to belong to four or five species only, mostly bacilli. At the end of two or three weeks, the original species had given place to others, mostly cocci, in a very similar way to the change which takes place in putrefaction. In fact, many of the organisms are identical with those which cause putrefaction. It will be seen, therefore, that no single species produces the complex chemical and physiological changes which take place, or the bodies necessary for the bating of skin, as some observers have supposed; but the various species succeed one another as the medium changes its reaction and composition, until finally the organic portion is resolved into the simplest bodies such as carbon dioxide, ammonia, and hydrogen. There is thus a moment when the dung is at its best so far as the bating action is concerned, and this moment is due to the vital activity of bacteria, and consequently varies according to the temperature and some other influences (electrical condition of the atmosphere, etc.). One may say it is at its best at about fifteen days in summer, and one month or more in winter. Puer which has been dried, is not so powerful in its action as that which is immediately made into a paste with water. It appears to lose its “nature,” partly owing to irreversible dehydration processes, and partly because some of the bacteria are killed. Plate cultures on agar from fresh puer (Fig. [17]), and from a puer wheel in use (Fig. 18), show the number of bacteria in the puer wheel to be much greater than in the fresh puer. Whence it is evident, that the bacteria continue to develop in the puer and to produce their various products, enzymes, etc. We have already considered the action of the chemical products, and in Chapter [V]. we propose to discuss the action of enzymes.