_———s 
* 
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47 
and it implied a voluntary act on the part of the animal, and it was 
with that meaning that it was generally used by writers on 
physiology. Professor Jones speaks of the ‘singular power of 
breaking off the limbs which was possessed by some of the 
erustacea.’’ The common lizard and blindworm were both well- 
known to possess this faculty, and some wonderful stories had been 
told respecting the former. All the writers spoke as if the 
animal had the power of doing this, but his belief was that the 
act, so far from being voluntary, was quite involuntary; that it 
was a mere spasmodic effort, arising from fright or other causes ; 
and that the animals had no more power in the matter than we had 
to stop the pulsation of our hearts, or to prevent starting or turning 
pale when suddenly frightened. Mr. Simpson then passed on to 
birds, respecting which be thought several things would be found 
which were not thoroughly known. First he asked what was the 
*‘oil-gland,” which was situated near the tail. It was usually 
supposed that this gland furnished an unctuous secretion for 
the purpose of oiling the feathers, and so enabling them to 
repel moisture so effectually that they were never wetted. Some 
considered it to be an excretory gland, and contended that 
if it was used for oiling purposes, dirt would adhere to 
the feathers. The Penguin, a thorough water bird, had no oil- 
gland, and many birds were so saturated with oil that an oil-gland 
would be unnecessary. It was probable that the manner in which 
the feathers were placed was the cause of the water running off 
them as it did. So long as a water bird was alive, it kept dry 
under any circumstances, but in case of death, or a broken wing, 
for instance, its power of keeping its feathers in the proper position 
_ to resist the entry of water ceased, and the bird soon became wet 
to the skin. This gland was absent in the Rumpless Fowl, and yet 
this bird kept its plumage in beautiful condition. Another point in 
connection with birds which was not thoroughly understood was 
their migration, which Mr. Simpson said was of two kinds—partial 
- and complete. Partial migration was effected by going from one 
part of the country to another ; but in complete migration the 
birds came over to our land from distant regions at one season, and 
left it at another. The difficulty of accounting for the migration of 
winter birds was great, because it did not appear to be necessitated 
either by change of food or climate. It seemed to be unaccount- 
able that birds, after having remained through the hardships of a 
severe winter, should leave us on the return of spring for colder 
climates, there to build their nests and rear their young. The only 
reason he could assign was, that they were unable to withstand 
' great extremes either of heat or cold, consequently they left the 
higher latitudes during the extreme cold, and the southern ones 
during the extreme heat. Mr. Simpson having briefly referred to 
