It is because of your bodies little-known secondary circulation system called the lymphatic system.
They can live inside the gastrointestinal tract or, the case of roundworms, in the lymphatic system.
It is only in Birds and Mammals, and especially in the latter, that the lymphatic glands form definite structures.
If one sister be sanguine in her temperament, the other must be lymphatic.
A second operation is necessary for the removal of lymphatic glands, probably on both sides of the neck.
But between them there was the difference of the nervous temperament and the lymphatic.
But women of a lymphatic temperament and of a relaxed habit of body are always injured by the bath.
It may be that Adrian scented a rival to his lymphatic emotions.
There are men in the prime of life, of a lymphatic temperament, whose blood seems to circulate moderato.
Thus no one is exclusively sanguine, bilious, lymphatic, or melancholic.
1640s, from Latin lymphaticus, from lympha (see lymph). Also sometimes used in the classical Latin sense "mad, frenzied," which was the primary sense of lymphaticus in Latin: OED reports this "difficult to account for," but perhaps due to association of lympha with nymphe; cf. Greek nymphian "to be frenzy-stricken."
lymphatic lym·phat·ic (lĭm-fāt'ĭk)
Of or relating to lymph, a lymph node, or a lymphatic vessel. n.
A lymphatic vessel.