Media. Growth rather slow, best at 37°. Above 47° no growth (Arloing).

They also grow more slowly but more luxuriantly upon feebly acid nutrient media (hydrochloric acid, tartaric acid). Grow more slowly but with greater vitality at 23° than at 37°. Especially good growth occurs in exhausted cholera or pyocyaneum bouillon either after or without filtration (Turró, C. B. XVII, 865).

Gelatin Plates. (a) Natural size: Very small, whitish, roundish, flat, rarely slightly elevated colonies, which do not grow perceptibly after a longer time (1, v).

(b) Magnified fifty times. Superficial: Roundish colonies with smooth border (1, vII e), but may present also wavy, scalloped, serrated, as well as fringed and torn forms (1, vi e). Color is gray to yellowish, structure delicately punctate to finely granular, usually transparent. Deep lying: Roundish to whetstone-shaped, rough or smooth border, somewhat more coarsely punctate than the superficial (1, VII i; vi i).

Gelatin Stab.-Stab: At first thread-shaped; after a short time there appear numerous small nodules in the stab (1, 1). Surface growth is like that in the gelatin plate. 1

Gelatin Streak.-Narrow, beautiful, delicate growth along the streak, beset at the borders with little nodules. Agar Plates.-(a) Natural size: As on gelatin plates. (b) Magnified fifty times. Superficial: Spherical colonies with delicately punctate edge, transparent, grayish-yellow, at first very delicately punctated, later (fourteen days) at times granular; frequently there is a distinct appearance of lobulation (1, VIII e). Deep lying: Smaller and somewhat darker (1, vì i).

Glycerin-ascites-agar.-Colonies distinctly more luxuriant. From the periphery of the superficial colonies there often extend outward numerous shorter or longer coiling chains, so that the colony appears not unlike a young anthrax colony. Also, the granulation in the interior of the colonies is somewhat more marked than upon agar.

1Liquefaction, according to German authors, is very rare. Pane saw the Strept. pyogenes from human abscesses at a temperature above 24° produce regularly liquefaction of gelatin which he had so prepared artificially that it was first melted at 30° (C. B. XVI, 228).

Agar Stab.-Stab: Thread-like, later sometimes granular (1, III). Surface growth: Very delicate growth, transparent, gray, irregular, unimportant. Atypically, the growth may be much more vigorous, with whitishgray color and smooth wavy border (1, Iv). Similar also on glycerin agar.

Agar Streak. As on gelatin. Water of condensation : Clear with slight whitish deposit.

Bouillon Culture. Varies greatly in the different forms, from diffuse cloudiness to the formation of a compact sediment with clear fluid (see p. 141).

Milk Culture.-Usually firmly coagulated in from four to twenty-four hours.

Potato Culture.-Invisible growth, at times entirely absent, rarely more luxuriant (compare p. 141).

Ac

Non-albuminous Medium.-Faint growth. Vitality.—In cultures usually only a few weeks. cording to Petruschky, cultures on gelatin, grown for forty-eight hours at 22°, if kept in an ice-box retain their vitality and virulence for months. The Strept. pyogenes belongs among the varieties that die quickly. Bouillon cultures, if oxygen is admitted, usually live only for weeks, but in hydrogen for months.

Resistance to Drying.-Vitality and virulence are retained several months, especially in dried pus.

Chemical Activities. (a) Chromogenesis: Almost always without pigment production; cultures were grown by Kruse and Pasquale in Italy with yellowish-brown to blood-red pigment. These were highly virulent, shortchained forms obtained from cases of tuberculosis.

(b) No indol, little sulphuretted hydrogen.

(c) Acid production from carbohydrates in our cultures was minimal; no gas formation.

According to Sieber-Schoumoff, certain cultures (Strept. erysipelatos and Strept. scarlatina) produce levorotatory lactic acid, others (Strept. pyogenes) inactive lactic acid from grape- and milk-sugar. All cultures produce, besides, some volatile fatty acids, poisonous albumoses, and of gases only carbonic acid, with the exception of the form found in scarlatina, which also produces hydrogen.

Emmerling's investigations (C. B. L. IV, 342) regarding the decomposition of fibrin by streptococci under anaerobic conditions gave the remarkable result that a solution of fibrin was effected. He found

succinic, acetic, propionic, normal butyric, and caproic acid, methylamin, trimethylamin, collidin, but no toxins.

(d) Toxin production: Upon albuminous nutrient media streptococci produce toxins, soluble in water and precipitated by alcohol. To collect them the cultures are killed with chloroform or filtered through porcelain. Large doses of the metabolic products cause suppuration and fever, and even death. This appears always to be only the action of protein.

Occurrence. (a) Outside the body: In soil, canalwater, once in a well (Landmann, C. B. XIV, 431), in the air of operating rooms, etc.

(b) In the healthy body: In mouth, nasal cavities, vagina, not rarely cervix uteri; at times, moreover, in a virulent form.

(c) In diseased human organism: The streptococcus is capable of causing a large number of diseases, namely, inflammation and suppuration in all parts of the body. It causes especially often the following diseases: Erysipelas, phlegmonous abscess, 1 lymphangitis, follicular angina, bronchitis, impetigo contagiosa, cellular pneumonia (Finkler), pyemia, septicemia, and puerperal fever. More rarely, pleuritis, pericarditis, meningitis, enteritis, etc., some cases of osteomyelitis, elephantiasis nostras (Sabouraud).

2

Recently, Escherich with his pupils has emphasized the significance of the streptococci in the diarrheas of children. The form isolated from such cases can not be imagined as a new sharply defined variety, in spite of slight deviations, but belongs in the division of the Strept.

pyogenes or lanceolatus. Escherich, Th., "Ueber Streptokokkenenteritis im Säuglingsalter." Separatabdruck aus Jahrbuch f. Kinderheilkunde, N. F., Bd. XLIX, 1899.

It is found in the blood and urine rather often, either with or without symptoms of a general disease.

The following also certainly depend upon Strept. pyo

1In phlegmons and abscesses more often the staphylococcus (Micr. pyogenes) is present, or a mixture of both.

2In the institute for infectious diseases in Berlin, Beck described a case of streptococcus infection (intestine, blood, viscera) that caused death in three days and presented during its course the typical picture of Asiatic cholera (C. B. XI, 632). Compare Tavel, de Cérenville, etc. (C. B. XVIII, 547).

genes infection: Some cases of nephritis, articular rheumatism, myelitis, and infantile paralysis. Mannaberg has found it in fourteen cases of Bright's disease (C. B. v, 93), whether as primary cause is questionable.

The streptococcus plays an important rôle in diphtheria, scarlatina, and phthisis. It accompanies the specific cause of disease, and markedly influences the disease-picture, especially the course of the fever (hectic fever is streptococcus fever) (Petruschky, Z. H. xvii, 59).

(d) In animals: As the cause of similar diseases (compare, for example, Strept. equi, p. 142).

In the vaccine of cow-pox institutes it is not uncommon, but usually possesses little virulence.

Experimental Observations Regarding Pathogenic Action. With living cultures. The virulence fluctuates greatly; even freshly isolated organisms may be very faintly virulent, and virulence for experimental animals does not prove virulence for man; with cultivation upon the ordinary nutrient media the virulence is rapidly lost. By repeated transmission through animals, a virulence which was high at first may be much intensified. Marmorek obtained cultures of such virulence that 1000 c.mm. killed almost all, and 1 c.mm. some, mice when given subcutaneously-i. e., quantities that contain only relatively few germs.

The virulence is well preserved, according to Marmorek, upon (1) two parts of human or horse serum and one part of bouillon; (2) one part of fluid from ascites or pleural exudate and two parts of bouillon, even after keeping two months in the incubator without transfer to fresh nutrient media.

In general the most susceptible to the streptococcus among animals are mice and rabbits; much less, dogs and rats (Pansini). Streptococci are still better tolerated by sheep and goats, and best by the horse and ass.

Knorr has ascertained the following principal points regarding the virulence: By repeated transmission through mice an organism is obtained which is very pathogenic for mice, but at the same time its virulence for rabbits was gradually lost. This is a strong indication that one must not found any species upon a specific virulence. The more

virulent a form is for a variety of animal, the more certainly it kills without suppuration, the latter being caused only by feebly virulent forms.

Almost all the diseases enumerated above may be produced experimentally in animals; the result in experimental animals depends very largely upon the virulence and amount of infectious material.

Also in man streptococci have been successfully inoculated (erysipelas, phlegmon).

Immunity and Immunization. If an animal resists an injection of the metabolic products, and has after a time recovered from the consecutive cachexia and loss of weight, then the dose may be increased and gradually a high degree of immunity be obtained. Yet the statements of Marmorek are contested, when he claims that horses and asses may thus supply a serum which cures human sepsis (Petruschky, Schenk). At any rate it has been shown, according to the investigations of Denys and his pupils (C. B. XXIV, 685), that the individual varieties of streptococci yield a serum that is active only against the particular variety employed in producing the immunity; thus also animals, in order to yield serum of therapeutic value, are to be treated with the most variable cultures possible of streptococci ("polyvalent serum"). Regarding the way in which the serum acts, compare page 97.

Special Methods for Demonstration.—Microscopic form and staining by Gram's method; agar plate in incubator; bouillon culture to obtain chains; animal investigation (mouse).

Forms and Subvarieties of the Strept. Pyogenes.

All efforts of authors to characterize sharply the forms of the Strept. pyogenes as varieties, subvarieties, or species, and to cover them with names are to be considered as failures. Countless transition forms and the enormous variability of all the properties make every classification appear insufficient. Even the separation from the Strept. lanceolatus is not always possible. Pasquale (Ziegler's Beiträge, XII, 433), Lemoine (H. R., 1896, 892), Widal and Besançon (H. R., 1896, 996), and Petruschky (H. R., 1897, 772) have all come to analogous results from their minute studies.

Behring and his pupil v. Lingelsheim arrived at the following useful1 division:

1 There are found by many authors a "Strept. brevis" without