The mammalian lacteal: its histological structure in relation to its physiological properties

One of us (H. W. F.) (7, 8) has already noted that the mesenteric lacteals contract on appropriate stimulation in a number of animals. He also observed in the guinea-pig and the rat that the vessels were rhythmically contractile. In the latter species the nuclei of circular muscle fibres in the lacteal wall could be seen in the living condition. The difficulties, however, of making out the part played by smooth muscle cells and nuclei in such contractions are very great in the living preparation. It was, therefore, resolved to supplement these observations on the living mesentery by others on fixed and stained material. In some cases the excised lacteal had actually been observed to contract in the living mesentery. The mesenteric lacteals of the cat have been taken as a type, and special attention has been paid to the distribution of smooth muscle fibres in the lymphatics in the various species studied.

CARBON DIOXIDE FROM THE NERVE CORD OF THE LOBSTER

1. The nerve cord of the lobster (Homarus americanus Milne-Edwards) is very delicate and can be used as a living preparation for only a few hours after its removal from the animal. 2. During the first hour or so after removal it discharges CO2 at a steadily decreasing rate beginning at about 0.20 mg. CO2 per gram of cord per minute and ending at about 0.07 mg. 3. This discharge exhibits a steady decrease in rate and is not divisible into a period of gush and a period of uniform outflow as with the lateral-line nerve of the dogfish. It terminates in a very few hours with the complete death of the cord. 4. Both handling and cutting the cord temporarily increase the rate of CO2 output. 5. The stimulated cord discharges CO2 at a rate about 26 per cent higher than that of the quiescent cord, an increase of about 1.6 times that of the increase observed in the lateral-line nerve of the dogfish under similar circumstances.