VIII.] MEAT RESIDUES 239 



the other. On the whole, the hop growers appear to 

 prefer fish to meat guano, but this is probably only 

 due to the greater regularity of the supply of fish guano 

 and its more uniform composition. There is no evi- 

 dence of the relative superiority of one over the other 

 which should deter anyone from buying whichever of 

 the two shows the lower price per unit of nitrogen and 

 phosphoric acid. The price of the better grades of 

 meat guano is raised to a certain extent by the fact 

 that it can also be used as a cattle, and especially as 

 a poultry food, in which case the nitrogen compounds 

 always command a higher price than when they can 

 only be employed as manure. 



As with fish guano, meat guano should be ploughed 

 in pretty quickly after it is sown ; birds find both 

 manures very palatable, and the rooks in particular will 

 carry off large amounts if left on the surface. 



Drkd blood is a product of the slaughter-houses, 

 which in its origin is closely allied to the meat guanos, 

 differing from them in the absence of bone and in 

 the nature of the proteins supplying the nitrogen. As 

 will be seen from its analysis, it is a rich fertiliser and 

 a very active one, because of the readiness with which 

 its nitrogen compounds are broken down into ammonia. 



Dried blood, however, comes but little on the 

 market and is rarely purchased by the farmer. The 

 total production is small and it is practically all taken 

 up by the manure manufacturers, who, because of its 

 richness in organic nitrogen and its good mechanical 

 texture, find it valuable for mixing with other manures, 

 when it is desired to raise the percentage of nitrogen 

 in a compound manure. 



Greaves may be regarded as a low grade of meat 

 guano ; properly speaking it is the waste from tallow- 

 making, and consists of the scraps of cartilage and bone 



