An ‘‘ Infected Ship ”’ means a ship which at the time of its arrival 
from abroad has on board a case of cholera, yellow fever or plague, 
or which has had on board a case of cholera or plague within a 
period of seven days, or of yellow fever within a period of eighteen 
days, prior to that time; and a ‘ Suspected Ship ”’ means a ship 
which has had on board during the voyage or during the stay of 
the ship in the port of departure or in a port in the course of the 
voyage a case of cholera, yellow fever or plague, but which has 
not had on board a fresh case of cholera or plague within a period of 
seven days, or of yellow fever within a period of eighteen days 
prior to the time of its arrival. If the replies to the questions 
(1) and (2) are satisfactory and the Boarding Officer has no reason 
to suppose that the ship is an infected or suspected ship, or has 
come from or called at any infected port, he issues what is called 
a ‘‘ Certificate of Pratique "’* allowing the ship to proceed. This 
certificate does not, however, exempt the ship from compliance 
with any special requirements of the Medical Officer of the local 
Sanitary Authority. (As to the issue of ““ Bills of Health” to 
masters of vessels clearing outwards, see page 87.) 
If, on the other hand, the replies are not satisfactory, and there 
is reason to suppose that the ship is an infected or a suspected ship, 
or has come from or called at an infected port, the Boarding Officer 
detains the ship and at the same time notifies the master that no 
person must leave the ship while it is under detention. The Medical 
Officer of Health then visits and examines the ship and, if he is 
satisfied, detention by the Customs ceases ; but if the ship is found 
to be infected or suspected, the Boarding Officer remains until the 
ship has been moored or anchored at the place appointed for the 
purpose under the quarantine regulations. Medical Officers of 
Health may visit and examine ships supposed to be infected or 
suspected, independently of the Customs officers. Penalties are 
recoverable under the Customs law for breach of the quarantine 
regulations. 
Signals.—Every ship (including fishing boats) arriving from a 
foreign port by day should hoist her colour, and every ship arriving 
after dark should exhibit a light, on reaching the boarding station. 
In addition, the master of an ‘infected ”” or a suspected ** ship 
must, when the ship is within three miles of the coast, or is within 
the limits of a port, cause to be hoisted :— 
(1) At the masthead or where it can be best seen, during the 
whole of the time between sunrise and sunset, a day signal, 
consisting of a large flag of yellow and black, borne quarterly ; 
or 
* The Certificate of Pratique must be delivered by the master with the 
Ships’ Report (see page 39).