EXPERIMENTAL AMCEBIASIS IN KITTENS 199 



that fixation must be performed immediately while the smear is 

 still wet. The general tendency of beginners is to make the smears 

 too thick. Another practice that should be followed without excep- 

 tion is the conducting of careful autopsies. Unfortunately many 

 students of general parasitolog}^ lack adequate training for this 

 work. Intestinal epithelium undergoes dissolution very rapidly 

 after death, hence intestinal tissue should be fixed immediately. 

 If the colon is opened out in a Petri dish in normal salt solution 

 the feces may be gently washed away and the lesions detected. 

 A binocular microscope may be used if necessary. Excellent fixa- 

 tion can be secured with hot Bouin's fluid poured on after the organ 

 has been fastened flat to a piece of cardboard. After half an hour 

 or longer transfer is made to 70 per cent alcohol in a vial properly 

 labeled. Sectioning may be accomplished without removing all of 

 the picric acid. For the preservation of liver tissue a thin slice 

 through an entire lesion and the peripheral zone is cut with a 

 sharp knife. Avoid handling with other metal instruments. Immerse 

 the slice immediately in a fixative, preferably hot Schaudinn's or 

 Zenker's fluids. After twenty-four hours of hardening, the fixa- 

 tive must be removed as directed in guide books. Lungs, kidneys, 

 spleen, etc., may be handled the same as above. Data are more ef- 

 fectively brought to the attention of other workers through the use 

 of condensed tables and graphical representations than through the 

 publication of detailed protocols. Furthermore, the making out 

 of such summaries gives one a clear perspective of his own work. 

 Training in statistical mathematics is very valuable in this field. 



SUGGESTED PROBLEMS 



It will be seen from the foregoing discussion that each step in 

 advance has reopened problems that appeared settled by earlier 

 work. For example, the successful cultivation of the amoebae sug- 

 gests that they may live within the lumen of the colon without 

 access to living tissue. Further experimental work on this question 

 is in order. As demonstrated by Dobell and Laidlaw (1926), 

 Yorke and Adams (1926) and Dobell (1928) the amoebae may 

 complete their life cycle in the test tube. This suggests an explana- 

 tion for the ''carrier'' condition in man but does not preclude 

 the probability that certain naturally occurring strains are less 

 pathogenic than others. Recent work by Dobell and Laidlaw (1926) 

 and Rees (1928) suggests that infectivity and pathogenicity may be 



