G. 11. F. Nuttall 
315 
development the tick is infective in the succeeding stage. When 
R. appendiculati(s\ for instance, sucks Theileria-lnfected blood as a 
larva the tick is infective as a nymph, or, having sucked infected blood 
as a nymph, it is infective as an adult. Whereas in redwater, the 
parasites persist in the blood for years after recovery, a,nd “ salted ” 
animals are capable of infecting ticks, the contrary holds for T. parva, i.e. 
when animals recover from East Coast fever they are incapable of 
infecting the ticks. 
The parasites are at first present in small numbers, but 5-6 "/o of the 
corpuscles being invaded. The number of parasites, as a rule, steadily 
increases until death, when 60-75“/,, of the corpuscles in the peripheral 
blood are found to be infected. We have never observed multiplication 
of the living parasites in corpuscles, but we have seen them in a few rare 
instances escape from the corpuscles into the plasma. The parasites 
1 2 3 4 5 0 
7 8 9 10 11 12 
13 14 15 16 17 18 
Fig. 11. Theilcria pari'a : (1-12) stained intracorpnseular parasites ; the figures arranged 
arbitrarily in a manner which would appear to indicate that they may divide into 
two or four parasites at a time, although division has not been observed to take place 
in living parasites; (13-18) Koch’s bodies, a series of stained parasites from a spleen 
smear, likewise arranged arbitrarily in sequence to indicate their probable mode of 
development from unicellular bodies; (17 and 18) represent the breaking-up of the 
Koch’s body and the liberation of its component elements. The black denotes 
chromatin, the stippling denotes the blue-staining protoplasm (Giemsa stain). 
(Original, and from Nuttall and Fantham, 1910.) 
move about actively within the corpuscles. Whilst the parasite is very 
pleomorphic, the commonest forms seen in stained preparations are ovoid 
or rounded and comma-shaped or clubbed. A proportion of the parasites 
are bacilliform. The appearance of the chromatin in some parasites 
‘ See Parasitology, vi. pp. 111-117, 195-203. 
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