They are especially remarkable for the small size of the body and the extension of viscera into the legs.
The soft integument and limbs of the mesosoma have been removed as well as all the viscera and muscles, so that the inner surface of the terga of these somites with their entopophyses are seen.
In the event of the host escaping being killed and eaten it is believed that some of these larvae wander about or ultimately make their way to the exterior, possibly through the bronchi; nevertheless it seems to be certain that they can only reach sexual maturity in the nasal passages of some carnivorous animal, and the chance of attaining this environment is afforded when the viscera of the host are devoured by some flesh-eating mammal.
It consists of a definite contractile sac or sacs lying on the dorsal side of the alimentary canal near the oesophagus, and in preparations of Terebratulina made by quickly removing the viscera and examining them in sea-water under a microscope, he was able to count the pulsations, which followed one another at intervals of 30-40 seconds.
From 1816 he published various papers in the Edinburgh Medical and Surgical Journal, which formed the basis of his Pathological and Practical Researches on Diseases of the Brain and Spinal Cord, and of his Researches on the Diseases of the Intestinal Canal, Liver and other Viscera of the Abdomen, both published in 1828.