112 EXPERIMENTS MADE ON SHEEP WITH THE INSECT, &C. 
could be seen which indicated that there had been an infection. 
— From the 3d to the 6th day the same. — On the 7th and 8th 
day. On many points upon the skin of the back the insects 
made their appearance, but without any change of the skin 
itself. — On the 9th day. Insects are seen in many places ; on 
the middle of the back, thick behind the shoulder blades, and 
many spots of the skin have become of a yellowish red colour. 
— 1 Oth day, as yesterday ; little spots are now formed, elevated, 
red, hard and inflamed, and there is a discharge of a gluey 
nature, which dries into thin scabs. — 11th day. The change of 
the skin continues to increase in a great many places ; under 
the wool the insects are discovered. — 12th and 13th days. 
The same appearances. — 14th day. The diseased condition of 
the skin shews itself in yellow, hard, and fixed scabs, under 
which the skin is bare, uneven and cracked, and shews a great 
many small and large insects ; for half an inch around these 
spots the skin is red and harder than the rest of the sound skin, 
and on all the changed points of the skin the animal manifests 
great irritability ; it tries to rub itself sometimes with its snout, 
and when rubbed with the finger it wags its lip, as is the case 
with all scabby sheep. — 15th and 16th days. The same con- 
dition ; where the scabs were taken off two days ago, fresh 
ones are formed, which spread themselves to fresh places ; the 
dark redness near to the diseased spots has greatly changed, 
and has become almost the colour of lead ; the inflammation 
goes on increasing, and insects of different sizes are present in 
abundance. — From the 17th to the 19th days. The diseased 
condition of the skin goes on increasing in extent in the same 
manner that it has done ; the neck is now affected as well as 
the back, and it is spread more backward ; and the spots on 
the skin are hard, elevated and inflamed, and of a bluish or 
greenish colour. Thus the scab has shewn itself fully esta- 
blished. By further observation up to January the 7th, 1828, 
the well-known disease was seen to spread more and more over 
this poor animal, and at last it had spread over the head, the 
whole neck, and back ; the legs and feet, however, remained 
free. — On the 7th of January it was killed for the purpose of 
another experiment. 
Experiment No. 9. 
Spontaneous Infection. — The interesting question having been 
excited as to the propagation of the disease, whether sheep quite 
healthy will become infected with the scab if they are mixed 
with scabby sheep and made to rub against each other. With 
a view of answering this question, the sheep marked No. 7 
was on the 24th of October put into the stall with the scabby 
