24 
THE ORGANIC CELL 
Immunity,’ by B. T. Terry, p. 310 of 4 Sleeping Sickness 
Bulletin,’ No. 29, which gives a most interesting account of 
a long series of experiments with different trypanosome 
infections, with special reference to the immunity following 
cure. Some of these experiments gave most encouraging 
results. A paper by Paul Behn in 4 Sleeping Sickness 
Bulletin,’ No. 35, p. Ill, on the same subject, and Bulletin 
No. 25, p. 127, should also be consulted. 
It is interesting but not very profitable to speculate 
upon the past history of immunity in nature. Such para- 
sitical forms of life as trypanosomes and piroplasms may 
have evolved, zoologically, comparatively recently or may 
have been recently promoted to a life cycle in the blood-stream 
of vertebrates. There are many blood parasites known, such 
as halteridia and certain leucocytozoons, and also certain 
trypanosomes, which produce no disease in the animals in 
which they are found at the present day, but they may have 
caused great mortality among these animals in the past, before 
their hosts developed an immunity and became tolerant of 
them. In 4 Sleeping Sickness Bulletin,’ No. 36, p. 142, 
some interesting information is given on 4 The Life-History 
of Trypanosomes in Vertebrate Blood,’ by C. Franca. 
The question of immunity therefore appears to be one of 
great importance. If wild animals can acquire an immunity 
in nature and domestic native cattle can also acquire immunity, 
is it not possible that the greatest success may eventually 
result from an artificially produced immunity ? 
THE ORGANIC CELL 
Part II. — Its Methods of Division and Status in the 
Process of Heredity 
By E. Wynstone-Waters, F.R.S.Edin., &c., Late Senior 
Demonstrator of Anatomy at the Royal College of Surgeons 
Edinburgh. 
As we saw in the last article the term 4 cell ’ is badly selected, 
and was used by the seventeenth-century botanists to describe 
