IOWA ACADKMY OF SCIENCES. 79 



sified according to whether they occur in normal animals, sozins; second, those 

 occurring in animals which have acquired an immunity, phijlaxlns. Sternberg,"* 

 than whom there is no higher authority in this country, says: "The experimental 

 evidence detailed gives strong support te the view that acquired immunity depends 

 upon the formation of antitoxine in the bodies of immune animals; as secondary 

 factors, it is probable that tolerance to toxic products of pathogenic bacteria and 

 phagocytosis have considerable importance, but it is evident that the principle role 

 cannot be assigned to these agencies." 



Sims Woodhead"" thus summarizes immunity: "It appears probable that 

 both the antagonistic action and this summative action are due to the bringing into 

 play, or the depressing, of certain specific functions of the protoplasms of the cells 

 by the products of different micro-organisms. It is not necessary that these func- 

 tions should always be manifesting themselves; after being once evoked and exer- 

 cised they may remain latent for a considerable period, and only be again called 

 into action under the regular specific stimulus. It is a case of wiitingonthe 

 looking-glass with ink and with French chalk — the ink is always in evidence, and 

 we might say that it corresponds to the enzyme, or the peptonizing functions 

 exerted by certain cells, animal and vegetable, whilst the French chalk, though 

 always there, is only brought out when the glass is breathed upon." 



BACTERIA OF THE INTESTINAL TRACT. 



In a previous paragraph I referred to studies made by Hallier and others on 

 Asiatic cholera, and the pleomorphism of bacteria. This disease, which for cen- 

 turies has carried away thousands of human lives every year, is certainly worthy 

 of the deepest and most profound studies of physicians and bacteriologists. That 

 the disease is contagious in its nature has long been recognized. The dis- 

 tinguished investigator, von Pettenkofer, long worked in vain for the specific 

 cause. His work on the spread and distribution of the disease is a most import- 

 ant contribution to the literature of the subject, especially his researches on the 

 relation of ground water and the "drying zone" to cholera epidemics. The 

 splendid achievements of Robert Koch who was sent by the German government 

 in 1883 to study cholera in Egypt and India made his name famous. On this 

 mission he demonstrated a specific micro-organism which he called the "comma 

 bacillus," but which belongs to the spiral forms and is known as Spirillum cholera 

 osiaticce. This germ was found in the dejecta of patients suffering from this 

 disease, in cesspools and water which received the dejecta, in milk, etc. It was 

 not as easy to convince scientists and physicians that the germ found by Koch was 

 the cause of Asiatic cholera, since Finkler and Pryoi'^*' found a germ in 

 Cholera nostras which appeared to be identical, and Deneke"" found apparently the 

 same germ in old cheese. 



Miller"* found a comtua bacillus in the human mouth; moreover, Klein, an emi- 

 nent English authority, claimed that Koch's material was entirely harmless. 

 Although the evidence of a spncific germ is not so conclusive in this disease as in 

 anthrax and tuberculosis, yet the accidental innoculation of a young physician in 



M M inual of Bacteriology, p. 262. 



«5Bacteria and Their Products, p. 379. 



«6Untersuchunfren uber cholera nostras. Deut. med. Wochenschr, 1884, No. 36. etc. 



67 UeDer eine neue den Choleraspirillen ahnliche Spaltpilzart. Deut. med. Wochen- 

 schr, No. 3. 1885. 



68Kommaformlger Bacillus aus der Mundhole. Deut. Med. Wocb, 1855, No. 5. 

 Micro-organisms ot the Human Mouth. Philadelphia, 1890. 



