FOUNDATIONS 11 



Harrison in 1907, the medium being lymph from adult 

 frogs. Next Burrows grew tissues from embryo chicks on 

 blood plasma in plate cultures. Using the same method 

 Carrel and Burrows cultivated tissues (kidney, spleen, bone- 

 marrow, etc.) of adult cats and dogs. 



Connective-tissue from the embryo chick has been kept 

 in culture for as long as eight years by Ebeling. An incuba- 

 tion of three days was observed by Busse before the cells 

 of fragments of rabbit's heart or aorta developed new cells. 

 The latter are branched and anastomose, but when bacteria 

 are placed near them they become detached from one 

 another and round ; they are attracted to the bacteria 

 (chemiotaxis) (see the Lancet, April 29, 1922, p. 856). All 

 these features are in keeping with what is familiar in the 

 study of granulation-tissue by other methods. When the 

 infecting organisms of molluscum contagiosum and kindred 

 affections are more generally appreciated, such cell-cultures 

 in practised hands may be useful in the study of some 

 details of the stages of infection. 



Cellulose and Chitin. Chemically isomeric with starch, 

 cellulose is one of the most abundant of the products of life. 

 Like starch it grows by intussusseption, and from it are made 

 a number of degradation products such as the jelly so freely 

 produced by many algae, etc. In the form of cotton- wool 

 it responds readily to the usual tests, turning blue with 

 iodine solution followed by sulphuric acid diluted with 

 water ; equal parts (Bower) or one of iodine solution to two of 



