8. THE REGULATION OF BREATHING
295
tion since an elastic recovery system can prevent undue energy loss in
reciprocating or tidal systems. In fact, the adult lamprey possesses a tidal
ventilation system, the water bcing taken in and ejected through the
external openings of the gills (Roberts, 1950).
hlany of the differences in pumping mechanism such as the presence
of velum, spiracle, and operculum depend in the first place on the
phylogcnetic position of the fish. Other differences of a less obvious type
arc related to habitats in which the fish live. Details of many of these
differences will be given in the following account, although the teleosts
will be treated in greatest detail because they are the most fully documented group of fish.
A. Teleosts
1. THE PATTERN OF WATER FLOW
a. General Features of the Breathing Movements and Pressures. It is
probably true to say that the recent developments in the study of fish
breathing movements began with the work of Woskoboinikoff and
Balabai (1936, 1937) and van Dam (1938). These workers introduced
the concept of a continuous gill curtain separating buccal and opercular
cavities. They also suggested that water flow over the gills was essentially
a continuous process even though the water entered and left the overall
pumping system in a discontinuous manner. Woskoboinikoff and Balabai
concluded that two pumps, one in front and one behind the gill curtain,
were responsible for maintaining the flow. Attempts to substantiate these
claims were made by measuring pressures in the two parts of the system
by means of simple water manometers. The views of these three workers
were summarized and extended by Henschel (1939) in a generalized
scheme of teleost breathing mechanisms.
Modern manometric methods were applied to the problem by Hughes
and Shelton (1958) working on trout, Salmo, roach, Rutilus, and tench,
Tinca. Pressure measurements in buccal and opercular cavities showed
that the gills offered appreciable resistance to water flow so that a
differential pressure was always found, usually with the gradient from
buccal to opercular cavity. Together with records of the breathing movements obtained from cine films, the pressure records offered good evidence of a dual mechanism responsible for maintaining water flow
(Fig. 1 ) . The breathing cycle was accordingly divided into two major
phases as the opercular suction pump (phase 1 ) or the buccal pressure
pump (phase 3 ) predominated, with periods of transition when the
295
tion since an elastic recovery system can prevent undue energy loss in
reciprocating or tidal systems. In fact, the adult lamprey possesses a tidal
ventilation system, the water bcing taken in and ejected through the
external openings of the gills (Roberts, 1950).
hlany of the differences in pumping mechanism such as the presence
of velum, spiracle, and operculum depend in the first place on the
phylogcnetic position of the fish. Other differences of a less obvious type
arc related to habitats in which the fish live. Details of many of these
differences will be given in the following account, although the teleosts
will be treated in greatest detail because they are the most fully documented group of fish.
A. Teleosts
1. THE PATTERN OF WATER FLOW
a. General Features of the Breathing Movements and Pressures. It is
probably true to say that the recent developments in the study of fish
breathing movements began with the work of Woskoboinikoff and
Balabai (1936, 1937) and van Dam (1938). These workers introduced
the concept of a continuous gill curtain separating buccal and opercular
cavities. They also suggested that water flow over the gills was essentially
a continuous process even though the water entered and left the overall
pumping system in a discontinuous manner. Woskoboinikoff and Balabai
concluded that two pumps, one in front and one behind the gill curtain,
were responsible for maintaining the flow. Attempts to substantiate these
claims were made by measuring pressures in the two parts of the system
by means of simple water manometers. The views of these three workers
were summarized and extended by Henschel (1939) in a generalized
scheme of teleost breathing mechanisms.
Modern manometric methods were applied to the problem by Hughes
and Shelton (1958) working on trout, Salmo, roach, Rutilus, and tench,
Tinca. Pressure measurements in buccal and opercular cavities showed
that the gills offered appreciable resistance to water flow so that a
differential pressure was always found, usually with the gradient from
buccal to opercular cavity. Together with records of the breathing movements obtained from cine films, the pressure records offered good evidence of a dual mechanism responsible for maintaining water flow
(Fig. 1 ) . The breathing cycle was accordingly divided into two major
phases as the opercular suction pump (phase 1 ) or the buccal pressure
pump (phase 3 ) predominated, with periods of transition when the