1266 Journal of Applied Microscopy 



Hum grows out over the wound. (3) Along the cut surface and in the region 

 just posterior to the point of least intestinal pressure, " embryonic tissue " is 

 formed. This embryonic tissue comes from the transformation of adult paren- 

 chyma cells. (4) The next stage in the process is the differentiation of the 

 embryonic tissue. This differentiation depends on the relation of the tissue to 

 the intestinal apparatus in general, and to the axial gut in particular. Tissue at 

 the anterior end of the axial gut forms a head, at the posterior end a pharynx, 

 and behind the pharyngeal region a tail. The reason for this relation of the 

 differentiation of tissue to the digestive system the author believes is to be found 

 in the action of " nutritional currents of a specific direction, intensity, and force." 

 The idea is a suggestive one and the experimental results give it considerable 

 probability. r. p. 



CURRENT BACTERIOLOGICAL LITERATURE. 



H. W. Conn. 



Separates of papers and books on bacteriology should be sent for review to 

 H. W. Conn, Wesleyan University, Middletown, Conn. 



Jordan. Some observations upon the Bac- Dr. Jordan has contributed an inter- 

 terial Self-purification of Streams. Jour. esting and timely article on the prob- 

 xp. e . . _7 , 9 . j^^^ ^j ^j^^ disappearance of bacteria in 



flowing streams by an exhaustive study of the bacteria in the Illinois river, 

 which has, in the last year, been converted into a drainage system for Chicago, 

 emptying into the Mississippi river, after flowing 318 miles. The pollution of 

 this stream with the sewage of Chicago has alarmed the people along its banks, 

 particularly in St. Louis, which city takes its supply of water from the Missis- 

 sippi river, some four miles below the outlet of this system of sewage. A study 

 of the bacteria of this river has been made with extreme care, and the bacterial 

 contents of the river, at different distances between Chicago and the Mississippi 

 outlet, have been determined. The result shows that the number of bacteria in 

 the river falls rapidly, and at its outlet apparently all of the bacteria which 

 came from the sewage of Chicago have disappeared, since there are no more 

 bacteria in the river at that point than are contained in the ordinary tributaries 

 of the river. The river, therefore, purifies itself and Chicago sewage does not 

 materially pollute the Mississippi river. The author also considers the causes of 

 this disappearance of bacteria without, however, reaching very positive conclu- 

 sions. He is inclined to believe that the exhaustion of the food supply is one 

 of the most important factors. h. w. c. 



Ford. The Bacteriology of Healthy Organs. Bacteriologists, in the past, have been 

 Transactions of the Association of American of the opinion that the organs of 

 ysicians. -39-9 • healthy individuals are sterile, and that 



it is only under conditions of disease that bacteria invade the tissues. This 

 opinion has been questioned occasionally, but no very definite conclusion has 

 been reached. Ford, desirous of settling this question, performs a long series 

 of very careful experiments. His method of work appears to be beyond criti- 



