Source, Etc

Irish moss, Chondrus crispus, Stackhouse (Class, Algoe; Subclass, Rhodophyceoe; Order, Gigartinaceoe), is not a moss, but a seaweed widely distributed on the northern shores of the Atlantic Ocean. It is collected for medicinal use on the north-western coast of Ireland, the coast of Brittany, and of Massachusetts in the United States. The plant, which is exceedingly variable in colour, in the amount of furcation, and in the width of the segments, grows just below low-water mark and is collected by raking. When fresh it varies in colour from green to dark purplish brown, but is bleached by exposing it to the sun and watering •it, the colouring matter, which is soluble in water, being partly washed out and partly destroyed by the treatment. The bleaching is said to be completed by chemical means.


The drug, which consists of the entire plant, is usually yellowish white in colour, translucent, and cartilaginous or horny. The thallus is rounded near its attachment to the stones upon which it has grown, but becomes flattened in its upper part, repeatedly branching dichotomously, the branches being sometimes narrow, sometimes broadly wedge-shaped. It has a slight odour of seaweed and a mucilaginous saline taste. A decoction made with 20 times its weight of water solidifies on cooling to a jelly, which is not stained blue by iodine (distinction from Iceland moss jelly).

Fig. 112.   Irish Moss (Chondrus crispus). Three different forms of the plant, a, b, c; a, with reproductive organs, natural size. (Luerssen.)

Fig. 112. - Irish Moss (Chondrus crispus). Three different forms of the plant, a, b, c; a, with reproductive organs, natural size. (Luerssen).


Stanford (1884) obtained from Irish moss 63 per cent. of a gelatinous substance which he termed carrageenin. This appears to be a complex mixture of carbohydrates; it yields by hydrolysis galactose, dextrose, and levulose (Sebor, 1900), and also hydroxy methylfurfuraldehyde (Muther and Tollens, 1904), and probably consists of galactan with glucosan and levulosan. The drug yields from 8 to 18 per cent. of ash, in which a little iodine can be detected, and about 7 per cent. of proteids.


Irish moss possesses demulcent properties. It has been given in pulmonary complaints and for chronic diarrhoea, and has been used for the preparation of a nutritious jelly. It is also employed for various technical purposes, such as calico dressing, etc, as a cheap substitute for gum arabic.

Varieties, Etc

Gigartina mamillosa, J. G. Agardh, which is occasionally found mixed with Irish moss, may be distinguished by its stalked sporocarps, as may also Gigartina pistillata, Lamouroux, but the latter is a rare British seaweed and its presence would indicate that the drug had probably been collected in France; the sporocarps of Chondrus crispus are immersed in the thallus, the surface of which is slightly raised over them.