Vietnam or Thailand ? Vote for the TOP Country of the Week !
Updated: May 9, 2025
From this point of view we might certainly say that a widely gaping fissure which had nothing prejudicial in it to Aratus Pisonii among the foliage of the mangrove bushes, was not suitable to the Ocypoda living in sand; that in the latter, in order to prevent the penetration of the sand, the orifice of the branchial cavity must be placed at its lowest part, directed downwards, and concealed between broad surfaces fringed with protective brushes of hair.
But as I was bending the feet of a large Sand-Crab to and fro in various directions, in order to see in what movements of the animal friction occurred at the place indicated, and whether these might, perhaps, be movements of particular importance to it and such as would frequently recur, I noticed, when I had stretched the feet widely apart, in the hollow between them a round orifice of considerable size, through which air could easily be blown into the branchial cavity, and a fine rod might even be introduced into it.
The branchial arches also, which separate the clefts, develop into very different parts. In the fishes they remain gill-arches, supporting the respiratory gill-leaves. Median section of the head of a Petromyzon-larva.
Some preliminary knowledge of embryology is essential to understand the formation of branchial fissures, and we refer the reader to any of the standard works on embryology for this information. Dzondi was one of the first to recognize and classify congenital fistulas of the neck. The proper classification is into lateral and median fissures.
As both auricles open into a single ventricle, this contains mixed blood. The dipneust form has now succeeded to the fish-form. In the further course of the metamorphosis the gills and the branchial vessels entirely disappear, and the respiration becomes exclusively pulmonary. Later, the long swimming tail is lost, and the frog now hops to the land with the legs that have grown meantime.
In Eriphia gonagra the entrant orifices of the respiratory cavity serving for aerial respiration are situated, not, as in the Grapsoidae, above, but behind the last pair of feet at the sides of the abdomen. Posterior entrance to the branchial cavity of Ocypoda rhombea, Fab., natural size. The carapace and the fourth foot of the right side are removed.
This sac-shaped organ, which is chiefly responsible for the solution and digestion of the food, has not in the lower Vertebrates the great physiological importance and the complex character that it has in the higher. In the Acrania and Cyclostomes and the earlier fishes we can scarcely distinguish a real stomach; it is represented merely by the short piece from the branchial to the hepatic gut.
The third branchial arch is only cartilaginous at the foremost part, and here the body of the hyoid bone and its larger horn are formed at each side by the junction of its two halves. They have been lost long ago. Moreover, the four gill-clefts of the human embryo are only interesting as rudimentary organs, and they soon close up and disappear.
One must, however, wait for a long time with these animals, when taken out of the water, before they open their branchial cavity to the air, for they possess a wonderful arrangement, by means of which they can continue to breathe water for some time when out of the water. Milne-Edwards has already pointed this out as a particularly remarkable peculiarity.
If the external orifice becomes occluded, there results a dermoid cyst. Tubulo-dermoids arise from embryonic ducts and passages that are normally obliterated at birth, for example, lingual dermoids develop in relation to the thyreo-glossal duct; rectal and post-rectal dermoids to the post-anal gut; and branchial dermoids in relation to the branchial clefts.
Word Of The Day
Others Looking